I've done a good bit of travelling around Guatemala (lived there for a couple of months!) some of the more remote border crossings into Honduras from there can be pretty dicey, I know some travellers are real big on the solo thing but I might be into heading further south than mexico with you if its something you might be into. By the way I have travelled the Continental Divide trail from here to Wyoming, I dont know what kind of bike you are riding but there are some incredible trails on the way down. By trails I mean forest service, secondary and generally shit roads that run through and over the Rockies. If you are riding a dual sport bike it would be easy enough and a good way to get some breaks from the highway. Anyway keep me posted....I live in Kalispell about two hours south of the canadian border near glacier national park. What kinda bike are you on anyway?
Have a good one