You can use a wick watering system.
Basiclly use a medium that wicks up water, just put a pan full of water under each plant and let it suck up the water as needed. The longest id suggest being away is 3 days. Id only put enough wate in each pan for about 24 hours. Then 2 days till it needs water again. So 3 days.
Remember, the bigger the pot, the more water it can hold, the longer you can go.
You can also build a system with actual wicks that would work for longer periods of time, since the plant wouldn't be sitting in water, suspend the plant over the water with the wicks hanging into the water, you want the wicks going a few inches up through the bottom of the pot.