45 mins is not too far at all~ It would make a great day trip!
I highly recommend Orfila winery in Escondido. The wife and I were members for several years when we lived in the area. They also have a tasting room in ocean side which is just a couple exits north of Carlsbad off the 5.
I live in Murrieta now, just north of Temecula and I will second cmullins recommendation as well, there are tons of great wineries up here. We are currently members at Avensole, which is obviously our favorite, but I would also recommend Doffo, Leoness and Robert Renzoni.
My favorite wines at these places are:
Orfila: Element 119 Pinot Nior, Sequestered Pinot Noir, Full Fathom Five
Avensole: Aventura, Double Creschendo, Cabernet Sauvignon
Doffo: Zinfandel, anything red, expensive but they are all amazing
Leoness: Zinfandel, Cabernet Sauvignon
Renzoni: Sangiovese, Barbera, Old Vine Zin
Keep in mind these are my favorites and my taste leans toward jammy, fruit forward mildly acidic, smooth finish reds. I don't really drink much white, but I have had the Chardonnay at all except Doffo and I would recommend them as well. Enjoy your trip!