If you stay right in Playa del Carmen there are plenty of non-inclusive hotels, though I think most are fairly small, I don't know how many guests you'll have. The cost can be quite reasonable, you can find good rooms between 100 and 200 per night, and that is per room rather than per person. There are many restaurants that you can walk around to, and I remember the prices being pretty reasonable (I was there in 2005). Some of them were really tasty, and had great ambience. Look on Trip Advisor to find good hotels. I enjoyed Playa, and it's not at all intimidating, even people who haven't traveled internationally much should feel quite comfortable. The main tourist area is totally walkable, no cab required, and several streets are pedestrian only.
I don't think you'd want a non-inclusive resort outside of town, it wouldn't be useful if there was nowhere nearby to eat.