[Quesita]

I second everyone else's suggestions. Lago Atitlan is a really amazing and magical place. Volcanos surround a huge lake, and little villages sit on the side of the volcanos. You can travel by boat from town to town. It is a few hours from Guatemala City, and I would strongly recommend at least a couple of nights there.

Tikal is beyond description. You need to fly there, or take a very very long road trip. I know some people do it in a day, and I think that is crazy. Depending on your travel style, you could stay within the national park itself, in very modest accomodations, or you could stay in Flores, which is a very sweet little town. I think that there are some other options as well, and new hotels that have been built in recent years. The ruins are so huge, and so extensive. If you decide to stay on site, I highly recommend looking at the moon cycle, and trying to stay during the full moon. Bring flashlights and sturdy hiking boots, and join the groups of people who climb up to the top of temple IV in the moonlight to look down upon the ruins and the jungle. There will be moments in which your eyes play tricks on you, and you will think that the city is actually alive with people living the way they did well over a thousand years ago...