My wife and I went to St Croix about two years ago, and the shore diving was amazing. We stayed at the Waves which is just down the street from Cane Bay. St Croix is perfect for shore diving, when we booked our trip I made a reservation for several days of boat dives, but after arriving found out that we could do so much shore diving that boat diving wasn't really necessary except as an occasional adventure. So, I tried to cancel the reservations with Cane Bay Scuba, and switch to a tank rental deal, but they were very unfriendly about the whole situation. I remained friendly, used them for rentals and even went on a couple of boat dives near the Salt River area - the staff was great. At the end of the trip, when the time came to settle up, they were going to force us to pay for all the days we had reserved (keep in mind, we never "missed" the boat, I told them as soon as I arrived we would not be going out as planned, but would do shore diving instead, and I got a reluctant OK at the time). Well, thankfully a local friend called the owner and let them know that screwing us was not good business, when we had tried to be as accommodating as possible, paying for services amounting to over half as much as we had initially reserved. That tension, really left a bad feeling with me for that trip, but otherwise it was fantastic.
We did shore dives from the Waves, Cane bay, North Star (a favorite) all the way to Carambola Beach resort, and Fredricksted Pier. I brought a sling with me and killed lionfish for awhile, but the black tip sharks would show up so fast, and several at a time that my wife starting getting nervous!! This was one of the best shore diving destinations I have been to, with the obvious exception of Bonaire. The wall is so close to shore and the clarity of the water is really great, I used Google earth to map out several dives just by eye-balling the reefs from satellite images. I would really love to go back, but I think it would be a little more fun as a group; generally my wife and I were alone. A car is really all you need, if you can get one that isn't too low to the ground that might help, but you really don't have to go off the road that much to access the dive sites.