The advantage of the wireless G standard is you can also you B devices.
If one of the pcs is near a phone line, plumb that one in with the router using cat5e cable.
This cuts the cost one a wireless adapter.
The speeds are all theoritical, so in practise you are unlikely to see top speed or anything near it. However the top speed of broadband is a 2 meg connection (unless you have a kindly company, or deep pockets)So you don't come anywhere near to busting wireless connection. Except through file transfer between the pc's.
B standard seems to be better at punching through thicker walls.
The printer should be available as long as it is connected to one of the pcs and it is set up to allow access to all.
I think the G standard should be fine at creating a network in the house. Because the range is less than the b standard if you have thicker walls you may find the garden may not have a complete coverage.