Ouch!  I have a couple of USGS Topo Series.  Waypoints, tracks, and routes can be transfer up or down.  The maps will not load on to a Garmin gps to my knowledge.  Only Garmin products or licensed third party products will load.
From the USGS support page:  
Support > GPS CompatibilityNOTE: Using TOPO! software, waypoints and routes can be transferred to and from your GPS unit, but the maps cannot be transferred or viewed on your GPS unit.