We will be taking bus from Basel to Mulhouse to pick up our car rental on Monday (French side). Are the car rental counters in the airport, or just follow signs? Thanks for any tips
If you are referring to Mulhouse airport, that would be EuroAirport Basel-Mulhouse-Freiburg, and is accessible by frequent busses from Basel SBB station. The car rental desks for French side are inside the Hall 1, Level 2.
https://www.euroairport.com/en/passengers-visitors/restaurants-shops-services/services/car-rental.html
https://www.euroairport.com/en/passengers-visitors/information/passengers/terminal-map.html
Basel-Mulhouse-Freiburg has some cool curiosities. Much infrastructure, like car rentals, are duplicated - one set on the French side, one on the "Swiss" side (in quotes, because although in France, it is Swiss for all immigration and customs purposes). Make sure you go to the French side. And yes, the counters are in the terminal.