download inSSIDer
http://www.metageek.net/products/inssider/ onto your wireless capable device (laptop) install it and run it. it'll search for all wireless networks within reach and it'll show you which channels each uses, 2.4GHz will range from 1-13. note channels then set your network to run using a channel number thats not in use.
match up 802.11 mode to your wireless devices, look up the adapters and their rates.
when testing your speed,
proof.ovh.net
regarding 5GHz & 2.4GHz.. unless your laptop has a 5GHz wireless chip/usb adapter/card you will only be able to connect to 2.4GHz networks