Instead I'd ask the driver for ADELITAS since I that's its name. Also, the yellow taxis have no meters. There are meter taxis to the right as you go through the Mexican customs/immigration area or the yellow taxis to the south. You'll be accosted by drivers as soon as you go through the second set of turnstiles after crossing into Mexico. You must negotiate the price in advance. You shouldn't pay more than $5 from the taxi stand to Adelitas. Maybe six. Since you're flush with pounds, you'll need to decide whether you want to haggle over a dollar. But if they ask for more, just find a driver who will take you. You'll find they speak enough English to get you where you need to go and know the numbers like a native English speaker. Some taxi drivers make sport of spotting newbies and trying to overcharge them. Some may also try to tell you Adelitas is closed [it never is]. Just insist on going to Adelitas and you'll be fine.
Even if you plan on only getting with street girls, you should start with a beer in Adelitas to see what it is all about. When you're ready for a street girl, exit the club, turn right onto the street, then turn right at the next intersection. There's a food stand and a bar, and from there you'll start seeing girls on the street trying to make eyes at you. Turn right into the next narrow street and the full alley is in effect. You should also check out the Hong Kong club on the alley and possibly catch the lesbian cream show if you're lucky. The other club I like after midnight is Chicago Club. You'll see that bar from the corner near Adelitas.There's really no reason to venture farther from this block as the neighborhood isn't that friendly, and the girls' quality diminishes quickly -- and some of the girls aren't actually girls. But in that block around Adelitas, you'll be fine. Many of the bar girls and the waiters speak passable English, the street girls have a more limited vocabulary limited to sucky fucky.
If you're going to get hassled by the police [the police in the zona area will leave you alone for the most part unless you're doing something stupid], it will happen late at night as you're just a few steps from the US as you're returning. Look confident like you're down there all the time, walk with a purpose toward California and 9/10 times they'll leave you alone. This works with the locals in the zona who will try to be your friend and guide you to a special girl or special bar. Just say no thanks. To be on the safe side, only carry as much as you need and they'll have nothing to steal. I try to give the last of my money to the taxi driver when he lets me out and walk into the US with only my passport and a smile from the good times I've had.
Again, with the weak dollar vs. the pound, you might want to pay for the $9 lot closest to the border at the Duty Free store. Less of a walk to the action, and you're back at your car quickly when you return. Just remember if you park on the west side of the I-5, you get back to your car by going in the pedestrian overpass you enter immediately to the right after you exit the US border station.
Don't stress too much, just be careful and aware. I've heard quite a few British and non-American accents inside Adelitas so you'll feel right at home.