Ok, this is our experience of obtaining Temporary Vehicle Import Papers at La Paz ferry terminal, and the ferry crossing to Mazatlan.

From La Paz, the ferry terminal is easy to find. Just follow the seafront road a few miles out of town. You'll see it, and probably a ferry or two being loaded/unloaded, as you come over the brow of a hill. You can't miss it.

Temporary Import Papers.
As you drive in through the front gate, you will see the two main buildings in front of you.

The left hand building has a car park in front of it with barriers, immediately on your left as you come in through the gate. Go into this car park and park up. Unfortunately you will have to part with 50 pesos on your way out but they kindly let us in as three bikes on one ticket.

Go to the building in front of the car park and head for the front right hand corner of the building. There will be windows there covered in posters explaining the TVIP procedure (helpfully there are some in English for those like us, with only basic Spanish), a payphone and some seats.

Wait your turn and talk to the lovely lady behind the counter. We only have basic Spanish and before anyone says anything - we are happy to use it, but the lady we saw spoke excellent English, which was very helpful. We don't know if all the staff speak English.

The basic procedure consists of filling out some simple paperwork and making a payment on a credit card.
The pieces of paperwork you will need to have are;

Passport
Tourist card
Original registration papers
Driving license (Disclaimer! I can't remember if we needed this or not! But maybe keep it handy? My memory fails me...)

The lady will need one B & W copy of all of these, it makes life easier if you get these in advance. If you can't there is an office round the corner that will make copies for a few pesos. It's just a pain in the arse to scuttle backwards and forwards.

The paperwork is very straightforward and to be honest the lady behind the counter filled it all in, entering the info onto the computer at the same time and handing things back for a signature now and again.

A payment must be made on a credit card, (you might have to duck inside the office to enter a pin number) for us this came to 6,359.37 Pesos each.
5,440 Pesos of this is your "bond", the rest is some fees.
Note: that figure may be different according to the age of your vehicle. We're on 2007 registered bikes. That year and anything later is the full fee. If your bike is older it's a little less.
When you leave Mexico, you have to go to the branch of Banjercito at your chosen border crossing and "cancel" this paperwork. Then you'll get your bond refunded back to your card, but not the fees of course. The lady gave us a map with the Banjercito offices that can be used. Not all branches can help.

You'll get some paperwork (keep it all) and a hologram sticker. If you're in a car or truck then the sticker goes on the inside of your windscreen. As we're on bikes we were advised to simply keep it handy but not stick it on the bike.

Once you have your paperwork and sticker you can head along to the other building (the right hand one as you turn in the gate) and through the sliding glass doors, the ticket office is immediately on your right as you come through the glass doors.

Buy your ticket for you and your vehicle. They will want to see your passport and your freshly minted Temporary Vehicle Import Papers.

Right, this is important!!!! Book early and get a cabin!!!!!!
More on this in a minute......

The ferry crossing.
When you turn up to get on the ferry, you go in the main gate and turn to the right. There are a couple of lanes and your vehicle and luggage may be half heartedly checked.
After that you are directed straight forward onto a weigh bridge. We had to pay a few pesos "fee" on the weigh-bridge. We were never able to ascertain what the "fee" was for. It wasn't much though, about 70 pesos each, and it's definitely a legitimate fee.
From there you can head to the relevant pier/quay and wait to be loaded on the boat.
From the weigh-bridge, it's not clear or obvious which quay is which for the different boats, so you'll have to ask a couple of times to make sure you're in the right place. I think there are only 3 quays so it's not too big a deal.

From there it's the usual ferry loading scenario, a guy checks your tickets and you are waved onto the top deck.
We were instructed to park with the other motorcycles and the bicycle touring guys and strap everything to the rail next to us (no tie downs in the deck). Straps and wheel chocks are provided, but they soon run out so you may have to ask for more. They squeeze the trucks in tight against you.
When we went back the following morning, nothing had fallen over and all the luggage was untouched, no one complained of anything missing. Even the bicycle guys who had no means of locking up their luggage.

Now........ It's an overnight ferry. Dinner and breakfast are included with the ticket - food but not drinks, these cost extra. The food was okay, but the small cafeteria gets crowded very quickly. Expect to queue and have very little elbow room.

We bought our tickets at the last minute and couldn't get a cabin.
If you don't manage to get a cabin then you have to spend the night on the passenger deck in the TV room. This consists of about 50 or so seats, similar to coach or airplane seats, that tilt back a bit. They are not that comfortable. We hardly slept at all. They play DVDs with subtitles on a big TV until about 10pm, then turn the TV off and dim the lights. The AC is left on and it gets quite chilly. If you have to spend the night here then keep your sleeping mat handy and a blanket or even sleeping bag, and just sleep on the floor. A couple of bicycle guys we spoke to slept out on the deck under the stars on their mats. Others went in to the cafeteria and slept on the benches around the edges. You'll need ear plugs!

If you don't get a cabin, try checking with the guy at the desk in the TV room about 20 minutes after it sails. Occasionally they have people not show up for their reserved cabins so they end up with free ones. Also, speak to everyone you can in the queue for the boat. The cabins all have four beds so if you can't find someone traveling alone or as a couple they may be willing to let you share.

Remember this is only our experience, but we hope it helps.

Tim and Lily. x