Making plans to visit Belize in May 2012 for 5 days. We'd like to visit the Mayan ruins, visit caves, scuba, horseback riding and beach it. Where would be the best location to stay to do these things. I'm thinking San Ignacio?

Other questions:

Best ruins to visit?
Best caves? (thinking ATM)
Best beaches?
Recommended hotels/lodges?

We are also thinking of going over to Tikal, Guatemala if that's worth it?

Thanks for any input!