what to say when the taquería line is moving too fast

Counter Spanish is shorter than the Spanish you were taught

A taquería counter runs on rhythm. The taquero is turning meat, calling orders back to the grill, making change and listening to three people at once. Long, complete sentences are not rude there - they are just slow, and slow is what makes the line stall behind you. This is why people who can hold a conversation in a classroom still freeze at a taco stand. The register is different, not harder.

The second thing that trips up English speakers is that politeness runs the other direction. In English, being polite means adding words: could I possibly get, would it be alright if. In Mexican counter Spanish, politeness means getting shorter and more indirect. Me da and le encargo are both softer than quiero, and both are two words. Porfa does the rest.

The exchange itself is almost always the same shape. You greet, you order by number and meat, they ask ¿con todo?, you answer, you pick a salsa, you say ¿me cobra? when you want to pay, and they say provecho as you leave. Learn the order and you can stop translating and start listening.