<<Disclaimer:  Verify this information before applying it to your situation.>>

In addition to eating salad (sans croutons) while traveling, I have found
that breakfast menus are often the most glutenfree...two soft-boiled eggs,
hashbrowns, bacon (if you can get past the fat), breakfast fruit, milk,
orange juice, etc.  Look for restaurants that serve breakfast all day.
Omelets are good, too, if you stay away from cheese sauces which are
usually flour based.

For lunch or dinner, try taco salad.  Ask them to put it in a bowl instead
of the taco shell.  Salsa is almost always wheat-free (but may have vinegar
in, so be careful if you are vinegar-intolerant).  Expensive but usually
gluten free is a broiled sirloin steak or charcoal-broiled hamburger.
Chicken seems to always come breaded.  Fish you must ask first (and if it
comes breaded even though they say it isn't or if it comes swimming in
an unidentifiable sauce, SEND IT BACK!)

Always always always tell the waitress that you have a wheat allergy (that
is more readily understood by the uninitiated than telling them you have
a gluten intolerance or celiac disease...sometimes they worry that you
will have a reaction right there in the restaurant).  Plus, if something
does come with the possibility of gluten (breading, sauces and croutons are
commonly seen on my plate even though I've asked about them beforehand),
if you've discussed it with the waitress, you can send it back without
guilt.

Be especially suspect about anything labeled 'wheatfree'.  I've often
been pleased to see something like 'wheatfree brownies' on the dessert
menu, only to discover that they use oatflour instead.

When all else fails, I have resorted to stopping at a grocery store for
apples and peanut butter, fresh fruit, taco chips, and cereal-free cold
hotdogs!  Not the greatest meal, but it keeps me from regretting it
the next day!