Advice for a beach in Mexico?

I am planning a week-long vacation to Mexico. I want to start with 4 days in Mexico city and then have 2–3 days in a quiet, non-built up beach. It does not have to be deserted and so remote that I would have to pitch a tent. I also want something pretty convenient to travel from Mexico City (flight/bus). Also, I much prefer a calmer beach where I can swim, sleep on the sand, run in the morning to a beach with a lot of waves and surfers. Except for snorkeling, I don’t do water sports. Thoughts?