Maybe try Angie's List or similar, where you can get reviews and references.
On a tangent, would they really need to come by that many times? If you watered well the day before you left, it seems like you could get by with just one visit, then water as soon as you get home. I don't have any really sensitive plants, but this time of year they all do fine with water every 7-10 days.
I wouldn't hesitate, for a two week trip, to soak them good before I left, then just water them the day I returned. Even if they wilted a little, they should bounce back from only one delayed watering.