This is a great ride report. Well written and great photos. I'm really enjoying it. And I'll second Dorian's recommendation for Tikal. There's a really cool place to stay on the road to Tikal in El Remate called "La Casa De Don David" that's really reasonable and has a great restaurant.
Do you know when you are going to get to Guatemala and what your route will be?
I have a bike in Flores I'm flying down to pick up. I fly into Guatemala City on the 19th and fly out to Flores on the 20th or 21st. I'll pick up my bike and ride it back to GC to meet a friend who is flying in on the 23rd. We're going to rent him a bike and head to San Pedro for a few days and then probably head to Monterrico until May 5th. He'll head back to GC to fly home and I'll head to the Mexican border to ride home.
If you're going to be in the area let me know and maybe we can hook up for a few cervezas