Sometimes. If its from somewhere that I cant really expect much better Ill normally accept that and just drink it (or leave it) - chances are they wouldnt care particularly or know how to fix it or be bothered to ask. For example, I had morning tea at a Starbucks a few months back which I knew was a risky proposition upfront; I asked for a double ristretto, the girl didnt even know what it was and had to be told how to make it and the pour almost looked like lemon cordial by the time she stopped it. Unless you want your $2 back, whats the point in returning something saying the grind is too coarse or the extraction too long if theyre just going to look at you blankly?
But somewhere thats using fresh coffee and pouring latte art (not that thats the only yardstick) are obviously trying to do something better than the next shop so theyre more likely to be receptive to constructive and informed feedback. It may be they were trying a new blend that day, or had just calibrated the machine or something (or had a work experience student on, shock horror!). Places that are trying to be the best normally welcome feedback on ways their product / service can be improved.