Even in southern California, where grocery stores are plentiful and diverse, it is difficult to find really good turkey breast. Deli cases are stocked with multiple choices of sliced turkey meat, which usually fall into two basic categories. The turkey comes from a real or rolled roast plumped up with broth, imbuing it with an unnatural flavor, or else the turkey is so processed that it looks like white ham and tastes like generic lunch meat.
The best sliced turkey breast I have found is available at the Katella Deli-Restaurant-Bakery in Los Alamitos. My mother, born in the Bronx and raised by German chefs, was thrilled to discover the Katella Deli when we moved to the area in 1964 and shopped there twice a month as long as she lived in Orange County. Their turkey breast tastes just like Thanksgiving leftovers if you had a professional meat slicer at home, but you can eat it year-round. You will pay for the quality - plus all the goodies from the adjacent bakery that you won't be able to resist.
Packages of sliced turkey breast from Trader Joe's are much more budget friendly and darn close to the homemade goodness of Katella's. You can buy regular or smoked turkey breast (pictured below) in slices that perfectly fit Katella Bakery's amazing long loaves of Jewish corn rye bread with carraway seeds. Just add Best Foods mayonnaise and your favorite fixin's - and you have a match made in sandwich heaven.