We did Mexico at 6-7 months (once baby was sleeping through night). 3 months is a little early but, depending on baby and your personality, could be fun but probably not relaxing. Sleep deprivation.
We stayed at an upscale resort that supplied us with the bottle sanitizer plus bottle warmer. We washed all his bottles using bottled water, then sanitized. I stopped breastfeeding at 6 months...if you're exclusively breastfeeding it could eliminate this hassle. I had to use a breast pump until I stopped at 6 months so wouldn've had to lug that with me if so.
What part of Mexico?