The best (and most consistent) chile rellenos preparation that I've had are from the La Nueva Cachanilla in Rosarito.
The batter is a perfect, a non-greasy robing of the soft, yet still toothy chile that retains its grassy, herbal spicy essence, even when reheated in the micro the next day. To die for!
Minor rant - I despise the cooks who are too lazy, too sloppy to remove the seeds.
Side note - yesterday I had a "taco rellena de jaiba" at the taco stand next to the Pemex in Primo Tapia/Cantamar, nine miles south of Rosarito, Baja California Norte. (For some stange reason, this item is not on the menu, just ask.) The taco was filled with a jalapeno stuffed with crab and lightly covered with batter. Heaven on a plate
Sitting at the picnic table on a wood deck overlooking the Free Road and the Toll Road overpass, watching the white/gray/black clouds drift across the hills of the northern arm of the bay, it was a great meal.
Total bill, including a shrimp taco, 35 pesos (approx. US $3.25).