Gotta do the update: They've improved so much since their first week. While I still think a bit more time for soft-opening might have been in order, they've listened to the feedback and made the customer service experience much better! Since my initial write-up, I've been back 3-4 times; a couple dining in and a couple doing carryout.
While eating in, they are still super busy pretty much from open to close, however the lines are moving much smoother and the food is coming out faster. I haven't had any issues with order accuracy and everyone is as friendly as can be in there. The tacos are still some of the best damn tacos I've had in the Concord area (read my original review for more details on the food, it's still all 100% spot on!).
Carryout was my biggest gripe about the restaurant and they have it figured out now. I'm not sure if something was wrong with their phones before or if they were just ignoring it. The manager I asked about carryout said they were taking carryout orders over the phone since day one, but countless phone calls went unanswered. This has all changed now as I've ordered twice over the phone and get through the first time. Both times my food is ready at the expected time and the carryout corner in the store moves much smoother.
I love it when I get to update a review for all the right reasons, great job T4L!