I suggest Searious Tours - up the beach just a bit from Ramon's - across from Rubie's. They were great! The tours are a bit better priced than Ramon's, and they bring along drinks and fresh fruit. Altun Ha is like a ruins "light" tour. It is not too taxing, and you get to stop at Maruba Spa (have a massage - great fun). Our favorite tour was The Manatee Tour through Searious. You get to snorkel, see Manatees and have lunch on a little island. Willy is a good cook and guide! Have fun!