When I arrived in Nantes and went for the check-in at my residence the woman started speaking to me in French and I did not fully understand what she was actually saying but the context was obvious. When she noticed that my French skills were in a bad shape, she slowed down a bit and it was a lot easier for me to understand her. One thing I noticed quite fast is that most people off-campus do not speak English in France and if they do they have a strong accent that is often difficult to follow up. So I was actually forced to speak French.
In my first weeks, I met a lot of Spanish and Eastern European students. To improve our French skills we decided to switch from English to French, as everyone actually had some French Skills, and it worked out quite well. Even some Germans decided to switch to French! So after the first weeks, I actually felt quite comfortable speaking French.
Being the only Erasmus student in my university class was a major benefit as well. I was compelled to speak French constantly while attending university, and it also facilitated my integration into my class. My class made a concerted effort to invite me to all of their planned social gatherings. It occasionally became a little challenging at these social gatherings. Due to the speed and usage of slang terms when my mates were chatting, I quickly lost track of the conversation when several people were speaking at once. So I had to ask for a summary from someone.
Overall, I believe I got along with my French rather well, and I have observed that some of my German and Spanish friends struggled more while speaking French, so I guess my high school French classes weren't all that horrible after all. But there were also times when I had the realization that I was still a long way from being a natural speaker of French.