We spent a wonder 10 days in La Zebra, Tulum, last year in August (2012) and I have to say we were pleasantly surprised about the cabanas!
We had a beach side (not beach front) cabanas still on the beach/sand, but not directly in front of the ocean to have an ocean view. However, the cabana was beautifully decorated with 2 double beds, netting on both, the living space was quite large for a cabana on the beach and the bathroom (although a bit on the small side) had a great flow and very, very clean!
We would not hesitate to go back to La Zebra, although it can get a little pricey with children (we traveled with 2 ages 10 and 13). They do not offer any breakfast specials included in the price of the room, so everything you want to purchase is extra and that can add up pretty quickly.
We tried their restaurant on the premises for both breakfast and dinner and although the food was really good on both occasions, the prices can get up there.
But it is on a great stretch of beach and you would not regret staying there!