David, not sure about Colorado. Probably would be fine. Many states issue a title same day. But that's a LONG (but beautiful) ride!
You will need insurance but will need a bike (or car) to list on policy before policy can be issued. I'm also not sure what the best companies are for NON US citizens regards insurance.
DR650's have gone up in price a bit for good, low miles used examples. The better ones are now closer to $4000, but you may see good ones from time to time at $3500. Don't buy an older beater ... not worth the trouble. Try for '06 or newer, under 15K miles if possible ... but the DR is good up to 60K miles easy.
(mine is at 65K miles)
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