Most of the time I really love Señor Taco. The food is good and the portions are big. The prices are great, too. They have awesome breakfast burritos (the size of Chipotle burritos) so I highly recommend ST for breakfast if you've imbibed the night before If you're a vegetarian like me, I recommend the bean tostadas. Doesn't sound like much but it's actually really good and only $2.99 on Tuesdays.
Another pro tip: the frozen margaritas are excellent. You may not think so since it's fast food, but I highly recommend ordering one if you eat in the restaurant.
The reason it doesn't get 5 stars is two fold. 1. Service can be REALLY slow. I sat in the drive through line for a solid 20 minutes tonight. 2. DONT use UberEats in Fountain Hills for Señor Taco. Just go get the food yourself. Two horrible experiences using this service.
All in all, a solid choice for grub in Fountain Hills.