My only regret when we were camping around the Yucatan and southern Mexico is that we didn't have enough time (like another three months) to go into Guatamela to see more Mayan ruins.
We managed a trip to Tikal in Guatemala and it was indeed magnificent. The trip from Guatemala back to Belize was dangrous but we managed to get to Belize City without being robbed.
Tikal suprassses anything we have seen in Central America except Teotihuacan outside Mexico city.