Mi Rancherito especial (if you're big you can eat it all). If you're not big you could split it with your wife.
Pupusas revueltas is also a great choice. Two will fill you up.
El Gallo Giro on University used to be my favorite until I started going to El Mexsal. I went there weekly for about a year or so. Now it's more like 1x/ month because I don't work as close. I went today with my son who also loves it.