The main tourist attraction is the town plaza and neo-Gothic church, which adjoins the plaza. The church is beautiful inside and out, with amazing wood carvings on its doors. Click here to see a map of sights to see in Santa Ana.
Banks and ATMs
The Oxxo convenience stores in Santa Ana all have an ATM machine, although the fee for withdrawing cash is considerably higher than using a bank's ATM machine (about $5, compared to $2 for a bank). There is a Banco Santander on the east side of Alvaro Obregon, just before you reach the plaza, and a Banamex on the corner just across from the plaza.
Also, to make you aware of a scam I once encountered, I was once withdrawing money from an ATM in a convenience store in Santa Ana and it appeared that the cash wasn't dispensed from the machine. After examining the machine more closely I found that someone had placed some double-sided sticky tape inside the dispenser, which had held the bills, and someone was waiting nearby to take the money had I gone to the store clerk to ask for assistance.
Groceries and Supplies
There is a small supermarket, Santa Fe, located just across the street from the town plaza on Alvaro Obregon. It carries a full selection of groceries, sundries, beer and liquor.
Snacks and Refreshments
There are at least three Oxxo convenience stores, as well as Fiesta convenience stores, in Santa Ana. Pretty much like convenience stores in the U.S., they offer a variety of snacks and beverages, albeit for a bit more than you'd pay in a grocery store. The "tipo Americano" coffee at Oxxo is good, and if you purchase beer they'll put ice in the bag for you, free of charge (just don't drink and drive).
The best (well, basically only) places to make a pit stop are the Pemex stations. Most stations have a separate building with bathrooms (banos). If you're not traveling with your own toilet paper (don't forget the TP!), the attendant will provide some for a nominal tip of three or four pesos.