To expand on Bill's post....... I have a higher end router (Cradlepoint MB1400)that does WIFI-AS-WAN and also will load balance across selected available networks. I have both Verizon and AT&T mifi hotspots and it uses data evenly between the two. I've also used it with CG Wifi and it's balanced between all three, but will provide uneven performance, if the CG wifi is spotty.
Also, the unit I have provides a super wifi signal, so I can use it sitting 2 sites over if I want to. If you are wanting to connect while outside, a good router is an excellent option.