What a lot of people don't mention is that a "quiet" café at 10 in the morning can be chaos by 3 in the afternoon, so it's worth going at odd hours if you can. Also, check the actual wifi speed before you commit to it - ask other customers or ask the owner to run a quick download test for you, because some cafés have a connection slower than a snail and it's gonna frustrate you when you need to upload files. And finally, smaller, lesser-known places tend to be cheaper and let you stay for hours without pressure, so you don't necessarily have to go to the popular chains.