I have been to El Portal multiple times and I really am not sure why. I think it has to do with the fact that there aren't a ton of options within a 2 minute walk of work.
I try to go at slightly off hours to avoid the lunchtime rush and at least haven't had any issues with service, although a good number of the tables usually seem pretty filthy and haven't been wiped off.
The food is pretty bland and uninteresting. I usually get a couple enchiladas, and the sauce, beans, rice, everything, just kind of melds together into a one-note bland mess. I guess I shouldn't be expecting much though when the food is so cheap. I guess that's a positive. One time the rice was under cooked and crunchy...I still ate it.
Unless you are starving, want Mexican food (if you can call it that) and are within a 2 minute walk I don't really see a reason to go here. Unfortunately, I seem to meet those 3 criteria every now and then.