1. Las Tortugas Deli Mexicana: there really is no Mexican restaurant like Las Tortugas. Unlike other places, Deli Mexican focuses more on "authentic" Mexican fare rather than the Tex-mex Mexican food we Americans are accustomed to. But don't just take my word for it. Listen to the owner.
As indicated, all the ingredients at Deli-Mexican are super fresh. Supposedly, if they can't find the ingredients that morning, they just don't make the dish. No abundance of melted cheese or grease. It has the best guacamole I've ever had, anywhere, period. I usually get the fish tacos or the fish salad. Either one is great. The green sauce they use on the dishes is the perfect compliment to the fresh fish. The only negatives are the prices are a bit higher than a normal Mexican restaurant. But that is to be expected given the high quality of food. No margaritas either and the atmosphere leaves much to be desired. But if food quality is what you are looking for (and you should be since this is a restaurant blog!), then this is the place for Mexican food in Memphis.
2. Las Delicias: Las Delicias is more of a "typical" Mexican restaurant but within this category it excels. The food is very good. I think that is mostly due to how well they seasoned their meat. Throw on some melted cheese and you've got a winner. I usually get the chicken burrito. The guacamole is also really, really good as well as the margaritas. But the big plus is the prices. Las Delicias is an awesome bargain. You can get out of there drinks, appetizer, entrees, tip & tax for under $40 for two people. A definite winner considering the great food.
3. Pancho's: here is a shout out to my childhood. That's a bit of a warning because this rating may be a bit biased. But hey, who dislikes Pancho's famous cheese dip or salsa? Well if you like that, you need to go to the actual restaurant. In my youth, there used to be Pancho's scattered throughout town: on summer, downtown, etc. All those have closed and so the only remaining one is in West Memphis. That's a bit of a trek, and it's not really in a great neighborhood either. But it's worth it. Pancho's is a true American Mexican restaurant, i.e. a lot of grease + melted cheese + horrible for you = tastes good. I'm a huge fan of the guacamole enchiladas. In fact, most Mexican restaurants don't even serve that dish. So it's a special treat anytime I visit Panchos.
4. Swanky's: In the past 10 years, Memphis has seen the infusion of dozens of fast foody type Mexican. Swanky's, Qdoba, Costa Vida, Moe's, etc. I think Swanky's is the best of the bunch. Their burrito bowls are great, and considering the fast food nature of the place, the ingredients are relatively high quality. I also like the vibe of the place for dinner, when it turns from a fast food place to more of a sit down type restaurant. And of course, I like the prices which are very reasonable. (Small aside, Memphis doesn't yet have a Chipotle, another of the fast food Mexican chains, but if it ever comes, it would sky-rocket up this list).
5. La Guadalupana: What would a Mexican restaurant list be without a restaurant on Summer Ave? What can't you get on Summer? Cars. Food of all kinds. Loans. Clothes. Drugs. Prostitutes. Ok, I'm not sure about the last two, just a guess. Anyways, you can certainly get Mexican food on Summer, and La Guadalupana is a great place to do so. It's reasonably priced and pretty large; so it's great for large groups or quick dinning. Burrito and enchiladas are good and are our normal choice. It also has more of an authentic feel than many other Mexican restaurants, probably because it's not a chain. Not the highest quality feel with respect to the interior and atmosphere of the place, so I wouldn't take a date there. But in terms of pure food and price, it's pretty good and always an option.