Looks like my wife and I may go there for 5 nights in mid April.
Wikitravel suggests that you stay at a resort and visit San Juan during daylight hours if crime is a concern. That would make my wife feel better. I’m more adventurous and, other things being equal, would prefer to stay in the historical part of San Juan.
Oh, absolutely you have to spend at least a day in Old San Juan. It’s just gorgeous. I could not get enough of the forts, personally. If you can, I also think a day in El Yunque is well worth it.
We had a resort near Fajardo and then went to San Juan for the last two days. Unlike an all inclusive, everything at the resort is pay as you go, thus quite expensive. For the most part I chose to have gambling money instead of drinking money. We drove thru the rain forest on the way to san Juan, it wasn’t difficult but it wad daylight. Didn’t do much other than hang around at the resort but we explored san Juan. It was enjoyable but pricey. And no money Exchange.
Old San Juan was awesome, and ime no more dangerous than any other urban environment. You don’t want to do stupid crap like flashing a bunch of cash around or wandering down dark alleys at 2am, but there’s nowhere you would want to do that. That part of town is prone to water mains breaking, though, so sometimes they go a day or two without running water. We were there the first 2 days of our trip and didn’t get a shower until we hit Vieques.
Vieques was simply amazing. If we were going back and only had 5 days, we would probably spend one in San Juan and the rest on Vieques. The beaches are gorgeous and when we were there (November) they were pretty much deserted, just us and the free-range horses. (With the horses grazing on seaweed on a deserted beach, it looked like something out of the first half of The Black Stallion. ) If you go, a kayak tour of the biobay is an absolute must. I’ll try to dig out the full name of the guy we went with, all I remember right now is that his first name was Abe.
And you have to take a drive down to visit at least one lechonera. Best. pork. ever.
Definitely rent a car. It’s quite cheap, and getting around the island without one just isn’t worth it.
Old San Juan is quite safe compared to other areas of the city. We stayed at the El Convento, which was wonderful.
Oh, very big tip: Do not order seafood while in Puerto Rico (or at least San Juan). Food in Puerto Rico can be really great, but there just is not the proper appreciation for good seafood. Not a single seafood-based dish we had on the island was of even mediocre caliber.