Currently, my favorite taco shop for carne asada burritos is Vaqueros a.k.a. "The Barrel". It seems that most taco shops are "hit or miss" or they change over time. "The Barrel" seems to consistently make a good carne asada burrito.
Another place that I had great carne asada burrito at recently was El Roberto's. It's obviously a branch of the Roberto's chain but it has the oldschool Roberto's flavor. However, I'm not sure how consistent the quality is as I have only been there once recently. It is located in a little stripmall off Clairemont Mesa Blvd near the 15 Freeway.