wireless printer on wireless n network?

I have a router which can support wireless b/g/n. BUT people tell me that the network speed is the lowest speed of any of your device.

For example, all my computers have wireless n support. But my wireless printer only supports wireless b/g. If they are connected to the same network, everyone will become wireless g........................

Is there any way to make all my computers connect with wireless n but my printer still connects with wireless g and they are on the SAME network?

Also I have two floors. How to set up the same network on two floors which can support a mixture of device of wireless g and n?