It's been a while since I've been down that way (too long), but here's my take on your ruins and wildlife questions.

I stayed for 2 weeks in San Pedro and took a couple of mainland tours from there. The Lamanai trip was a great day trip. They pick you up at your dock, boat to the mainland, up a river, take a bus, then another trip by boat to the ruins. It was a great trip and I highly recommend it. I also highly recommend Tikal in Guatemala. I took it as a day-trip. It was incredible but it would have been better if I made it an overnight. If you're in Belize, you're in the neighborhood and it really is something you should see. Go. You won't regret it.

The Tikal and Lamanai trips aren't real wildlife treks, but we saw quite a number of animals in their native habitat such as howler monkeys, spider monkeys, cuoti, a green jay, a toucan, a (big) crock on the bank on the boat ride back from Lamanai, numerous birds. The boat driver knew where there was a bat "hang-out" so we saw a bunch of bats hanging around. The best wildlife item we saw wasn't actually an animal. In this case, that's probably a good thing. During the Lamanai tour, there was a rain storm (whoda thunk, rain in a rain forest? ;-)) and after the rain stopped, we continued the tour. Not five minutes back on the hike, we spotted a very fresh jaguar print that had to have been made sometime just after the rain stopped.

A lot of people say the Belize Zoo is not your typical zoo and I've heard people really like it. I didn't see it so I can't tell you from personal experience.

Take a Blue Hole dive trip. The dives that are typically done during this trip are the best I've had. The lunch break we took was on Half Moon Caye which serves as a bird sanctuary for a few species of birds (spinakers, blue-footed boobies and one other, if I'm not mistaken). There is a tower you can climb to the canopy level and see them flying and nesting in the trees.

Here I am rambling. Can you tell I'm wishing I could get back there?