We go to "The Plaza" all the time at the Methuen location.
Yes- the tableside guac is where its at- aliong with great margs.
I am a huge fan of the shrimp salad, burrito san jose, and Flag encheladas.
A good, fresh, tasty meal for cheap!! Usually under $40 for 2 people!!
There is one on the Methuen MA/Salem NH border, and yes a chain.
When they first opened, they were awesome. Huge menu, fresh, gorgeous ingredients (the roast pork fajitas were a work of art).
They've gone through two menu changes (not seasonal, global) in the last year and it's been hit or miss. Some of the bad changes have been trivial (the crema based sauce they'd give you with salsa as a condiment for the table is gone), some are big (menu items taken off, quality of meat is worse). The one sure bet is the homemade tableside guacamole, which is made fresh and to your exact specs...it's incredibly good.