An important piece of having coffee in the morning is making it part of a routine. If you're predictable in your habits, you start to see the same people in the same space at the same time, and you get to be something of a regular.
If you're careful, and switch your morning allegiances from time to time but still visit the old haunts often enough, you can be what passes for a regular long after you stopped coming every day.
How often, then, do you need to show up for people to remember you? For that I turn to structured repetition, and the power of priming memory periodically to strengthen it. Supermemo, a software package for memory improvement, has a nice paper on using Supermemo without a computer, which specifies a pattern of repetitions and intervals to get details into memory. The table of intervals specified says that you review materials at this pace:
4 days, 7 days, 12 days, 20 days, 1 month, 2 months, 3 months, 5 months, 9 months, 16 months, 2 years, 4 years, 6 years, 11 years, 18 years
Which suggests that a well-timed practice of showing up at a cafe, introducing yourself to everyone, learning their names, and them coming back at precisely timed intervals to repeat the process would be enough to make you a regular in no time at all.