How many 'locations' you can post depends on whether you use design time Markers or run time Markers. I am aware of one developer who used more than 7000 run time Markers but I expect with that many Markers the app runs slowly. Why not try to see how many you can use before the app breaks.
The above examples use a CloudDB, something similar could be done using GoogleSheets. There are several discussions about using locations and GoogleSheets in the community.