Mexican Honey/Babymoon!

Hello! I'd love to get opinions on the best place to travel in Mexico in early to mid October. We're looking for a beach town that is very chill (not interested in bars/clubs being a main attraction), where we can relax at a resort but also explore surrounding towns by car. I'd love to go to a place that isn't super touristy, but still has a good amount of hotels to choose from as well as access to the city's cultures and authentic food. Adventures (hiking, cenotes, rainforests, etc.) would be a big plus too. Does anyone have a spot that comes to mind? Open to any of Mexico. I will be 19 weeks pregnant at that point so traveling shouldn't be a big issue. Thank you!!