i have to agree with kaliraksha, however July is extremely hot here in Mexico, and it is everything but peaceful, because it is high season, so if you're looking for somewhere really peaceful there may be some options, but it's just gonna be harder to find them

so, other than the heat, scorching sun and lots of tourists, you can also try in Los Cabos, it's the "in" place for honeymooners right now there's this super beautiful place called "las ventanas al paraiso" hotel, as well as some other beaches in Jalisco, near Puerto vallarta, here i can tell you that the One and Only Palmilla resort is AMAZING, and the Hotel Basico in playa del Carmen.
oh well, i could go on and rave about lots of places in Mexico, because there's just so much to do see, do, and go here but i think it depends also on what you wanna do in your honeymoon, the kind of place you like (beach, jungle, rainforest, etc).
this is a pic of Las ventanas al paraiso in Los cabos, this is where i want to spend my honeymoon