I'm not sure I'd pass up Uxmal, but bus to Palenque is several hours. Then overland bus to Flores and on to Tikal. I strongly recommend staying in Tikal National Park. Cannot overstate how wonderful it is to spend the dawn and dusk hours inside the park, surrounded by the jungle. Tikal is worth at least a couple days roaming around. If you stay in the park, you can miss the hoards or tourists coming in from Flores, 50km away. They get to the park at 10am or so and leave by 4. If you go out to the park at 530-6am and watch the jungle come alive and wander the pyramids early, it is an unforgetable experiece. After 930-10am, wander back for a beer to your room. Laze about until well after lunch and hit the trail back to the park by 3pm and wave bye-bye to the tourists. Then watch dusk fall from the eastern acropolis. Magic!
=Terry
btw - the Lonely Planet Central American thorn tree is a better place to ask questions about Tikal and the Mayan ruins.