If I were new to TJ I'd park on the US side and take a cab to Adelitas, and won't hear anything else from the taxi driver, like trying to take you to a massage palor..... just say Adelitas only nothing else, even if he claims they are closed, say still take me there....... pay $5 dollars only.
From Adelitas(AB) it's in the middle of the zona. They alley is around the block either turn left or right stay on the sidewalk, and you'll see all the SGs. But if you want a BBBJ from an SG, it's a little bit hard to get. Most girls will do a CBJ asking for $10 more dollars but will always accept $5 dollars, or 50 peso( $3.50 for a better deal) But many SGs don't do BBBJ, although some do, but you must search or ask around. Generally the SG's range from so-so to bad, and only last a few minutes, so I rarely ask for them from SGs, as they are really about about a " quick fuck."
The best bet if you want a BJ is try a bar like AB. In fact I would recommend Hong Kong as just about all the girls do BJs there, and many will do a BBBJ. Tropical is good for for BBBJ, although I ran into a few girls there that refused to do BJ's altogether in that place, but within the last couple of years almost all girls will do BJ's now.
But for first timers I still recommend AB since it's a very gringo friendly bar, and the service is easy to get, and decent. I generally don't like to negotiable what a girl will do or not do, but if your time is limited, then I would suggest you ask the girl will she do a BBBJ?