I've only been to one restaurant in Coatepec (and I can't remember the name - but it was a large old house in the centro) and the trout tacos dorados were excellent.
In Xalapa, my favorite lunch or dinner is at La Sopa (Callejon del Diamante). They are right next to the Fonda, mentioned by Paul. Unfortunately, the last time I was at the Fonda, I received service so bad that I don't plan to return.
I also like Los Itacates which is near the School for Foreigners on a side street between Zamora and Xalapenos Ilustres (I think) - excellent lunch menu, also very good breakfast.
Salta de Xala on Murillo Vidal was also a good lunch, but I remember less about it, so I plan to return.
Asadero 100 is a chain, but I'm very happy with a good tequila and sangrita, an order of nopales and a taco. If you manage to catch the orchestra in town you can go to the concert (on a Friday at 8:30pm) and then after cross the street to the Asadero 100 - usually the musicians do the same.
At the Paroquia I've had hit and miss experiences with the food - chicken soup - very good, arrachera - very bad. But, they always have horchata de coco - sooooo goooood.
I'm not a big fan of the Churreria del Recuerdo, mostly based on the fact that their churros aren't very good in my opinion (but after the Bombilla in Guadalajara, I'm spoiled). Their enfrijoladas are good, as I remember.
Good luck and if you find that place in Coatepec with the trout tacos, please post the name!
The best cup of coffee in the world is in La Parroqua in Xalapa. Try a lechero. There are several
very good restaurants in the calliejon diamonte. The first one on the left "La Fonda" is quite good.
The lady who owns it has a couple of other restaurants, one of which, "Churraria de requerdos"
specializes in old time dishes, such a guisados etc. Coatepec has a great cup of coffee in the
"Arco de Noie" which is on the plaza. I expect you will get along fine since you know how to spell
Xalapa. Don't miss the ceramic codex display in the Anthropological Museum.
Pablito el gordito
I didn't make it to Xalapa this trip, so I don't have any specific dining recommendations. I was in Xalapa 10 years ago, and had forgotten how good the food was in that region. Where I was (Orizaba), on each table they put a salsa macha, which sometimes comes encacahuatada - both are amazing, though the latter was truly wonderful - nutty, spicy, smoky, and salty. I brought some back to share with my husband so that we can figure out how to make it ourselves. Also, the morning coffee is good, strong, smooth.
Even their simple salsa verde was super-flavorful. My favorite meals were a pollo stuffed with jamaica, with a slightly creamy purplish salsa on top - slightly sweet and slightly sour. The salsa likely had been been made with jamaica, but my husband later told me that there is a berry from that region that they may have used as well that gave it both the color and slightly sour flavor. REALLY good. The other one that was very memorable was a pollo en salsa limon, which suprised me because the salsa limon had been cooked with chunks of red pepper, onion, and melon, all served in a 'bowl' of iceberg lettuce. It was a beautiful, colorful dish, and delicious as well. I'm not usually one for cremas, but the crema de elote and crema de esparragos turned me on to cremas. I'll add that every meal was between $5-$8, including drinks, so I wasn't eating fancy (though not at absolute dives either). Many restaurants were advertising mole de panza, which I didn't try but which must be a regional specialty (perhaps b/c Orizaba is so near Puebla?).
The only bad meal I had was a place someone recommended for the colonial atmosphere and free wifi- bad, overpriced food and weak coffee.
Enjoy your trip - can't wait to hear about your eats!