Microchips

No. The veterinarians do not have scanners.  I purchased tags produced by  tagsforhope.com because they have more information than the regular metal ID tags.

Oh wow.. okay. My little dog is so obnoxious with chewing and licking tags that I don't put tags on her..but I do have my phone number embroidered directly on her collar. She tends to escape given any opportunity and one time I got her back because she ended up at a vet that scanned her.. that was before I got the collar with my phone number on it. I'll definitely be more worried about her escaping after moving to PR. I'd like to figure out a way to put tags on her in addition to the embroidered collar, but I'm not sure how to do it where she can't reach them. She's a little Shih Tzu with such a short face that she can nearly reach her own neck.

I think I need a "slide on" dog tag.

They started selling those things a few years back, only to find (unbeknownst to the people who actually purchased them), that they were not valid in PR. Even if they were, you'd have to be lucky enough to get a vet (or Vet's clinic), conscientious enough to scan the pet.

That's too bad.. back to the old fashioned collars and tags... unfortunate if someones dog slips out of their collar.

I have a secure yard now... one of the reasons my wife and I left Rincon. Rentals were higher, and the yard we had was HUGE, but not secure, so whenever we left home, the dogs had to be inside... and I'd be stressing for my dogs, if away too long.

Yes, many vets do have scanners.  Any that sell microchips should have scanners, but it is best to ask the question.  Sadly, the "shelters" and rescue organizations do not have scanners, so if your dog is picked up the odds of the microchip helping to reunite you with him are zero. 
All my dogs are microchipped anyway (you have to start somewhere).  But I suggest you also use a metal buckle collar embroidered with your phone number, for the best chance of reuniting with your pet should he ever get lost. 
If you are in the north west, Hospital Veterinario San Francisco de Asis in Hatillo does sell Avid microchips, and they have a scanner.  They are also the only 24 hour vet in this area.
I should also mention that there is a new law under proposal(protector 1631) that would require microchips (among other things).  So if passed, this would no doubt increase the number of vets and shelters with scanners, so keep your ears open.

When we first arrived here in PR, we were shopping in Walmart.  They had a vending machine that for $5 printed a stainless tag - it has my name, local address & phone #.

The first few weeks here, he (my dog) took to running off down the beach, to roam, play with kids down at the park, etc.   At least three times, people called me to say that they had my dog!  Drove down to wherever  and picked him up.    He stays home better now that he is used to his new home, but the tag has really paid off in keeping track of him ( he's such a friendly numskull! )  A tag can be drilled and attached at both ends with stainless or copper wire to make it more secure and not dangle. 

I also have a slide on the collar type tag that can't be pulled off.   I have also heard of people getting the dog tattooed - but that's not my choice.

At any rate - you need some type of ID with contact info.