Not sure if it's good news or bad news that it took me nearly 9 months of living in JP before I tried this place because now I'm an addict.
I am a big Tacos Lupita fan, but let me share this: Lupita's pupusas don't even come close to these treats! Seriously. I'm not sure how best to describe why - the flavors seem so much more vibrant - the fillings really shine through. I've tried cheese and pork & cheese, they also have bean & cheese. Anyway, I could guess that it's the made-to-order thing, but I'm pretty sure that these are made to order at Lupitas as well (at least in Somerville). I do like the flavor of the sauce at Lupita's better, but they are very different. Lupitas sauce is thin, more like a stock, and really tastes of meat. La Pupusa Guanaca has sauce that has more tomato and spice, and a lot thicker.
Your to-go order at LPG will come packaged up like this: pupusas in foil, one plastic baggie of slaw and one plastic baggie of sauce. It's fun for assembly when you get home.
Oh, and then there's the empenadas. I cannot believe a chicken empenada can taste so good. It's finely ground like a sausage and so flavorful. I went back and tried a beef one, and while it was good, it didn't compare. I still might like the beef filling of the empenadas/pastellitos at Estrella better, but overall, I prefer these fried delights over Estrella and Madrego's.