The Chili's restaurant chain offers a nice collection of margarita options, all of which (in my experience) are good choices. However, my favorite on their menu is the Presidente Margarita, which by the way is Trademarked to Chili's.
Served on the rocks, this premium blend is smooth and balanced with excellent flavor and comes to the table in its on shaker, so you actually get a couple of glasses out of one drink. Its available in every Chili's regardless of location and so far, I have not found any real differences between restaurants.
But its worth noting that the Montgomeryville, PA location is pretty unique in the fact that the restaurant connects with a hotel. Thus, if one was to over-indulge, once could simply walk out the side door, down the hallway and into the lobby of the Courtyard By Marriott hotel and book a room for the night. No need for a designated driver when you have a designated hotel room!
Checkout the recipe for the Presidente Margarita.
The Presidente Margarita is top notch and gets a 4 lime rating.