Trip tips for off-beach snorkeling, sand, restaurants, some nightlife?

I'm researching a late-March or early-April trip for my husband and myself from the Washington, D.C. area to the Caribbean. I think I've decided upon St. John based on my priorities (below), but I'd love to hear what other people with experience with Caribbean travel have to say. I've never been.

I've been scouring the web, reading strings of conversations on sites like Fodors, and checking out homeaway.com. But I was wondering if anyone out there has a specific condo, hotel, area on the island to recommend based on our priorities. I'm also completely open to ideas of other places in the Caribbean all together, but most signs so far have pointed to St. John.

Our priorities are, in this order:

1. Good, off-beach snorkeling;
2. A sandy beach;
3. A few good to great restaurants/bars we could walk to;
4. Some decent nightlife--though not packed, touristy madness; and
5. Some decent hiking.

We open to staying at a hotel, but might prefer a condo (grilling, kitchen, cooking with some of the local ingredients).

I'm capped at about $2500/week.

Thanks everyone! I really appreciate your advice!