Went to Tulum Ruins as they were only 10 mins away from where we were staying. Definitely worth a visit. This is one of those trips you can do on your own. Just jump on one of the buses and ask to get dropped off. The cost to get in wasn't much, can't remember what. They were selling a trip from our hotel which amounted to the price each of what we paid altogether for 4 of us, there and back (approx $20). Although there are heaps of people queuing to get in, the ruins are spread over a good sized piece of land so plenty of room. Well maintained area. The view from the ruins down onto the beach is lovely. You can go for a swim, as quite a few people do, but there are quite a few stairs down.