My wife and I stayed in Alba for four days in December 2012 -- a fantastic place to visit. Yes, you do need to call in advance before visiting wineries, and it helps to know Italian (or have someone call on your behalf who does). These are the wineries we visited:
** Produttori del Barbaresco in Barbaresco -- the biggest winery we went to, fantastic co-op with great wines to taste (and buy) and very interesting to learn how the co-op was founded, how it operates, etc.
** Silvio Giamello (La Licenziana) in Barbaresco -- visited because he'd been recommended as an under-the-radar but great producer. Located in an unmarked small farmhouse/compound. I felt guilty taking up his and his wife's time with our tasting because they really are a very tiny family-run operation, but it was a delightful experience talking with them and bridging the language difference to learn about what it's like to do what they do -- everything from the vineyards they own to raising children. Wonderful wines, too.
** Giuseppi Rinaldi in Barolo -- brilliant traditional winemaker, though I think his daughter increasingly runs things. Took us into the cellar, gave us barrel tastings, wonderful.
** Bartolo Mascarello in Barolo -- also a brilliant traditional winemaker, also run by his daughter. Outstanding.
** Castello di Verduno in Verduno -- a bit larger, more commercial operation but I enjoyed their wines, too.
I wanted to visit G.B Burlotto in Verduno because I love their wines, but they were closed. Also tried to visit Luca Roagna's winery, but he was in the U.S. at the time.
One other thing -- if you can, plan to buy some bottles and take them back. (We brought some "wine diapers" and stuffed them in our luggage.) Not only are they great but relatively cheap. For example, we bought the Bartolo Mascarello Barolo for 34 Euros, which is 1/2 to 1/3 what you'd pay to buy it here. You might even find some wines that aren't exported to the U.S.
One of the best things is to drive around and visit the different hilltop towns like La Morra, Monforte, Serralunga, etc. They will likely seem pretty empty, but they're beautiful with spectacular views, and many have great restaurants, too.
Enjoy your trip!