Concur about La Rochelle - lovely place, been there many times. You can get away with just a little Franglais with the refueling guy and the Tower most definitely speak English. As for joining, since it is a controlled field but usually little traffic, depending on the runway in use, I tended to join at whatever was the most expeditious point. So coming on a direct track from Nantes airspace, means right base for the westerly runway and left base for the easterly runway (can't remember the vectors). Never caused a problem since I almost invariably was the only aircraft in the circuit.
Parking overnight on the grass is free. Parking on the tarmac is not...
Caution: to the north of La Rochelle is a reasonably large swampy area - ie on the other side of the bay (the ariport lies on the south side of this large bay). In certain weather you will find low mist in this area - to avoid it extend east over the ocean otherwise you may find yourself in IMC close to the airport, which is never much fun but in fact you will generally find better conditions at the field, so don't divert too early!
Have fun.