Provisioning for the Trip

According to what I'd been told, one should a) bring everything and b)bring nothing, everything is available. This is typical advice from cruisers and should be graded before accepting. The reality is, bring everything you might need, other than water, which is easily available.
Lowest on the list is the advice of those 'who have heard', or who preface their advice with 'I've been told...'. Interestingly enough, their advice was by far the most negative, in all areas. After years of interviewing people, I'm not really surprised by this - people usually remember the most negative of what they hear, as opposed to the good stuff.
Next up on the list is those who have been there, but only to the resorts, travelling by air. While their experience is barely relevant to my needs, there are some kernels of info here. Interestingly enough, these people didn't present their information as 'fact', but simply for what worth it might have.
At the top of the list for obvious reasons are those who have actually sailed to Cuba! Unfortunately, I've found few of those here in Georgetown, which is often the southern terminus for North American cruisers.

Provisioning: I was told fresh meat and eggs were not be permitted on entry. That was not the case, in fact, the inspection was pretty casual. Produce that is not fresh won't make the cut though but frozen meat is no problem at all.
Beef is unheard of, pork rare, lamb, chicken and fish the mainstays, if you can find them for sale. Milk is powdered, if you can find it. What we consider basics, such as sodas, bread, soap, salt and pepper....many of these items are luxuries in Cuba. Vegetables are available at outdoor markets but bread is rationed and hard to find. Note to self: buy oven, learn to bake. Asking the marina manager or someone with some authority wherever you are at will usually yield you a couple of loaves. Don't expect to pay for them, but have a nice gift handy for your benefactor. On the other hand, fishermen will often trade for what you have. If you do trade with the locals, be circumspect about it, because it's not allowed. Your local friend will find themselves in trouble with the authorities.
I traveled with as much frozen meat as I could fit in the freezer, lots of UHT milk, a couple of loaves of bread, and plenty of staples such as spaghetti, canned meat, lots of propane and, essentially, enough provisions to get me through one to two weeks without (much) self imposed discipline. My theory is that, where there are people, there will be food, making it a (hopefully simple) matter of finding it. In any event, I needed to lose a few pounds!
One group of fishermen provided me with enough lobster tails and a lovely red snapper to account for four or five meals, so I actually ended up back in the US in good shape.
Bring lots of soft drinks and drink crystals, and stock up on these in the US. Prices in the Bahamas for soda are sky high. Fruit juices are available in Cuba, but again are not cheap.
Beer is inexpensive, as is rum. If you want wine, you'd better carry it with you.
Toothpaste or any sort of personal care item should be brought with you. If you want to be especially nice, pick up inexpensive razors at the dollar store back in the US, along with soaps and shampoos, as gifts. Anything for children is needed and welcome. Aspirin and otc drugs are also quite welcome: I gave a bottle of acetaminophen to one local who was suffering from a bad back. Cuba's much vaunted socialized medical system had no drugs for him.

Everything I've read says that one can travel about in Cuba, and so it is. Car rentals are easily available; again, ask the marina manager about this. Prices depend on the season and can be quite expensive - you're best off sharing with other cruisers if you can.

One person has told us that 'she heard' that shopping was impossible for her friends as they were not permitted ashore. That in fact is the case. There must always be someone on board your boat, unless you are tied up at one of the international marinas or at a Guarda post. Keep in mind, there are people who will attempt to make it to Florida in an inner tube raft, or a waterproofed 1957 GMC pickup. Your boat is a real temptation to freedom and this is partly why the Guarda watch over you so closely.