Mexican food restaurant- Carne Guisada if prepped without potatos, Carne Asada, fajitas, and Menudo (if you find the right joint, it's very primal friendly). All of this is assumed to be ordered sans tortillas, rice, beans, etc.
Steakhouses- Go nuts- just ask for a salad of veggies instead of whatever version of potato they bring you.
Japanese steakhouse- They'll gladly cook whatever it is without sauce and add extra veggies for you.
By far the most primal friendly restaurant I've been to was a local hibachi grill. I got chicken and calamari and they cooked it absolutely perfectly. Even asked me whether or not the sake and oil they used to cook with were ok. I asked them for no rice and extra veggies and got a heap of veggies 3 times as large as anyone else.