Oreo will make this task a little bit easier. When it scans for nearby WiFi, it also will assess what kind of speed you can expect from it. It won't tell you a detailed result of its test, but will instead describe the speed as "slow" if its under 1Mbps, "OK" if it between 1Mbps and 1.5Mbps, "fast" if it is between 5Mbps and 20Mbps and "very fast" if it exceeds 20Mbps.
The change is rolling out now with Android Oreo 8.1.
Public Wi-Fi can be spotty. For the first time, #AndroidOreo 8.1 lets you take out the guesswork & see the speed of networks before you hit connect. Rolling out now: https://t.co/lSzvCFgNk7 pic.twitter.com/60EmoPxUX4-- Android (@Android) January 22, 2018