Elotes are a very popular street food served all over Mexico. It's roasted corn on the cob, slathered in butter, mayo, cheese, and chili. The type of cheese used is cotija cheese, which is a dry, grainy cheese from Mexico. It's fairly salty and is used in many traditional Mexican dishes.
The thought of eating something so artery-clogging may not sound ideal, but if you've never had elotes before, you are missing out on a treat. I wouldn't eat this everyday but when I do have it, I enjoy every single bite. At Dona Tere, an elote is only $2, and they top it for you when you order it. If you prefer to eat your corn sans cob on a stick, you can opt to order the elote en vaso. They cut off all the kernels from the cob and serve it in a cup with all the toppings mixed in for $2.50. I personally prefer to eat it on a stick, it's funner that way and you get to enjoy it a bit longer.
Dona Tere also serves other very affordable street food from their stand. Another popular item is their mango, which is served with chile, lemon, and salt for only $2. It's even listed on 7x7's 100 Things to Try Before You Die list! You can also order tamales with chicken, pork, cheese, or jalapeños. The tamales are only $1.75 each, so try a couple. In fact, most of the items they serve are $2 or less so try a bit of everything!
The Dona Tere stand is located in the Mission at the corner of 21st St. and Alabama, just look for the truck with the blue canopy over it and people eating corn on the cob.