Based on the raves on this board went to Del Valle last night. Better than average inexpensive mexican, but nothing unbeleivable (although I should say that having lived in both New Mexico and Texas and traveled throughout Mexico I have relatively high standards for mexican and all its derivitive cuisines).
First, it doesn't have a liquor license, so we BYOB from the bodega on the NW side of 10th & 47th. I remember it just having negra modela & corona.
We were served chips and watery salsa as soon as we sat, which helped as we surveyed the menu. We sat in the right side restaurant space (left side is takeout), which was small, clean, & well lit. Out of the 10 or so tables there, there were only three tables (including us) with people at 8:30 PM. One table was mexican, which we took as a good sign.
We ended up ordered two platters: the spicy chicken and chile rellenos (~$10 per platter). The chicken was OK; two pieces in a red chile sauce that was not that spicy. The rellenos were very good. Very savory, covered by good red & green chile. The rice and beans that accompanied both platters bordered on institutional. Also served with corn tortillas that were not the freshest.
We also ordered two tamale verdes (chicken) (~$2 per tamale). These were quite good. We ate one with our meal and took the other home and enjoyed it the next day. It had good flavor depth.
Overall, based on the tamales and rellenos (I have yet to find great rellenos in NYC), I would go back and further explore the menu. There may be gems there that we didn't hit. However I would not say its a must visit based on my experience.