Here's the answer I got from a fellow employee who's from Puerto Rico:
Hi Kathy,
In general it is OK. You will find curb cuts and wheelchair accessibility in
most hotels and " tourist" areas in the San Juan Metro area. The main mall in
San Juan is all set up for accessibility and it even has a covered valet parking
area. Although Old San Juan is where you will find the old churches, forts, art
galleries and historical places, the city itself was built on a hilly area. If
your friend is staying at a hotel he or she may ask for the availability of
special tours and buses.
I hope this helps.
He was very gracious in answering my inquiry right away!
Kathy S.