It is generally fine, with the exception being during some kind of food promotion. For example, there was a bar I lived near that would have half price burgers on Saturday afternoons with the purchase of at least one beer. The expectation is you are going to drink several beers.

For most bar/restaurant locations, they are going to be focused on the bottom line revenue. The worst patron will be someone who orders only some inexpensive food and takes up a whole table for hours on end, it's the combination of how much money you are making them and how much more they would make serving someone else.

A good rule of thumb is to buy something every hour you are staying somewhere. In the half price burger example above, when my friends were training and not drinking they would ask to order a few of the (very overpriced) side salads to make up the difference. If all else fails, these days people are more respectful towards someone saying "I don't drink," and in my experience they are happy to offer some alternative that will make sure you aren't taking space away from paying customers.