It’s probably too late to reply to this post now, since you probably already decided where to go. I’m in the program now and lived in the student housing.
Housing in Old Town Alexandria and in the neighboring areas is high. The campus is in the middle of a city and 10 minutes to DC, so you can’t expect it to be very cheap. The student housing is generally offered for one year and the price is much lower than the average rent options. However, the MLA program is generally two to three years so you want to take that into consideration. I think if you want to live at the Gallery, you most likely can. I’ve only known of a few people who weren’t able to get into the student housing, but this was because they applied for the housing very late, like close to Aug.
You can message me if you have any more questions.