Adequate medical care is available in all major cities in Mexico, in rural areas facilities may be more limited. In general, private hospitals offer better care, though at a great cost, than public hospitals. These private hospitals feature the latest modern facilities, equal to the standards in the USA or Europe.
Mexico has many fine doctors, and many also speak good English. If you need an English-speaking doctor in Mexico you may ask in your hotel; they should have the contact details of a local English-speaking doctor that they will have on hand for their guests. The same goes for dentists.
Pharmacies are ubiquitous across Mexico; even the small towns have one. You'll always be able to find a 24/7 pharmacy somewhere locally in Mexico.
Be sure you have insurance to cover any medical costs during your stay in Mexico.