You can either look up the specs on all your devices and you will very liky find that they do not support N since it is the newest
when looking for a router / access point for your home network make sure it support N as well as all the older specifications.
Most router are fully backwards compatable and support all older specs. as well as N
802.11n is backwards compatible with 802.11g. I have a combination of 802.11g and 802.11n devices connected to my 802.11n router at home including my wife's laptop that has an Intel® PRO/Wireless 3945ABG Network Connection and my laptop with an Intel® Wireless WiFi Link 4965AGN. Both laptops connect without any problems to the 802.11n router. Of course, my laptop gets an "n" connection and my wife's laptop gets a "g" connection. I also have several other devices at home such as a printer, blu-ray player, , iPhones, and a Wii that all connect via 802.11g. All my "g" devices connect to the "n" router without any problem.
I went ahead and got a router (Linksys WRT610N) that has simultaneous connections on the 802.11a and 802.11g frequencies. Since our laptops have adapters with an "a" radio, they get there own connection. The separate connection means that the laptops are not competing with all the other devices for the Wi-Fi connection. Everything else in the house connects to the "g" radio.
Because of the MIMO improvements in 802.11n, you might find that you can get a better connection to your 802.11g devices in parts of your home where you did not get a good connection before. I have no regrets on the decision to buy an 802.11n capable router.