I highly recommend Condesa Amatlan 84. It's an unassuming little spot, but it's extremely welcoming and Paul, Alicia and the rest of the staff couldn't be nicer. But the biggest reason to stay here is the amazing location in the Condesa neighborhood. You won't want to leave! If you're planning on visiting the pyramids, make sure to go with Efren, the hotel's go-to tour guide (as long as you speak a tiny bit of Spanish). Dude is hilarious.
One watch out - the neighbor's dog starts barking kinda early each morning. If you had your sights set on sleeping in, this might be an issue for you...