Ello me again!!!
One of my favourite excursions whilst in Mexico was the Jungle Tour. There is a group of say 5 couples, and each couple gets to drive their own little speed boat. You all follow in a long line through the lagoons which is fantastic, and then you pitch up and go snorkeling. It was great fun.
Myself & OH will be going Mexico again for our Honeymoon and plan to do Xcaret, which is an Eco park. It has lovely caves which you can swimming through, quad bikes, and even zip lines through the jungle. Can't wait! Here's a linky
http://www.xcaret.com/Water_activities/underground_river.html
Also swimming with the dolphins is a must, such an amazing experience.
We didn't take much spending money with us the second time as we didn't do anything whilst on holiday. I think we took around £700.00 the first time. If you search for the excursions online you can get an idea of what the prices are.
Also I definatly reccommend lots of $1 notes. These are great for tips. If you tip a maid or waiter etc, you will be treated like royalty forever! The mexicans are such appreciative people, 50p goies a long way!