As long as you stay within the city center, it isn't going to be a problem! We took buses around the place and it was fine as well, but definitely watched our belongings and stayed on the way to landmarks/beaches only.

I don't regret going at all, as it was quite an interesting place and honestly you get beautiful views pretty much everywhere. Just if you like hiking, don't be like us. Go when it's not too hot, as likely the best places to visit around there are the Parc les Calanques, as well as a bunch of parcs/places around the region in general (the only pink lake in Europe is like a 3 hour drive away!).