We spent almost 4 weeks at J's place and we had a very good experience. We came with my 3 children (aged 3 to 10) to spend time with family and go to summer camps, so we spent a LOT of time in the house. J and her family welcomed us on the first day and they were consistently available and helpful throughout our stay - we had a couple of minor issues and they took action immediately, solving problems right away. The house worked very well for us - it had more than enough bedrooms and beds to provide space and privacy for all of us. The beds are great - hard enough to take care of our backs but soft enough to be very comfortable. The kitchen was well equipped and we cooked at home almost every single night. Internet was good and we were able to do many skype calls back home without a problem. We didn't use the patio much - we stayed during the heat wave. The neighborhood is nice - walking distance from Caltech and with several restaurants and supermarkets within a few minutes ride.
Overall, great experience.