I stayed with my friend Giorgia in Lo's appartment for 7 days.
It was very pleasent. We had all we needed to cook some nice meals besides the great dinners we had in the city.
Belleville and the park arei very nice areas and I can recommend to stay at Lo's place. (it is nice and clean ;) is cosy and great location.
The subway system is so easy. Buy the Paris Visit pas for 3 zones and you can move around infinitely in the city.