To get to know La Rochelle there is only one way: walking. If you don't like to take long nice walks, you possibily won't get to know La Rochelle and therefore, won't like it.
If you are interested in small historic town's dynamic this is the right place. The city is filled with monuments and has that great historical look most french towns have. Millions of bakeries and markets are spread all over it, making it easy and cheap to experience french meals and goodies - chocolates, pies, and etc.
I recommend, above all, the La Gignette pub. It reunites students from all town, including foreigners making it a fun and nice place to hang out.
Enjoy the cheap books available at street book sales, if you are learning french or already knows it, you cannot waste the chance to buy all kinds of french literature for less than four euros.
You have all kinds of restaurants available, with all kinds of food, but if you are looking for a simple cheap meal make sure to find Creperies and pâtisseries - I assure it will be a delight and a nice way to experience local meals.
And although La Rochelle is a wonderful city both to live in and visit, in my opinion it is not a place will put for a week on your travel intinerary, I believe two or three days are more than enough to get a taste of the town and to get to know it well.