I use, and really like, the Mapswithme app which uses open street maps data. What I like most about it is that it downloads maps for entire states or countries on to your phone, so you can use them when you don't have cell service, just gps. The maps are actually not that large, most well under 100MB, although CA is the largest at 233MB. I do some manipulations on my computer in other software in order to get exact routes onto my maps, but if all you want is to use the gpx files on ACA's website, which only have the waypoints (may not exactly follow the roads), you can load the ACA gpx file into Google Earth, then save it as a kmz (or kml) file. You email that file to yourself, and open on your phone to get it into Mapswithme. The you can see the waypoints in Mapswithme on your phone when you need them. You can also create paths in Google Maps, save them as kml's and import the same way. There's a Lite version of Mapswithme that's free if you want to see what the maps look like, the sizes, etc., but in order to import tracks, waypoints, etc, and to get other functionality, you have to get the Pro version, which costs $5. Well worth it in my opinion.