Our daughter is covered by Tricare. I checked with theTricare Service Center before leaving the US. I was informed that the closest Tricare service center is located in PR. The pharmacies here will not accept your insurance card. However, if you have a recurring prescription you can use the mail order program.
As far as the facilities, well, my daughter required an appendectomy last year. We used Tricare Standard. We were presented with the "TOTAL" amount of the bill (by the director of the hospital) and paid the required 20% deductible before she was released (Bournigal in Puerto Plata). Needless to say, I later received a letter at my US address. The amount of the bill had doubled. In addition, the amount of my check for the deductible had "APPARENTLY" been lost and not posted (although it cleared my bank account). BTW, "ALWAYS" use a check as a form of payment although they insist upon a credit card.
After this experience, my advice to anyone using Tricare would be to obtain insurance here which is fairly cheap. Your deductible will be much cheaper than the 20% of the inflated prices for services they charge Americans.