GPX Files:

You can right click the mouse on the file and open with notepad.If you want to really get a good look at the file use Extra Poi Loader to look at it. http://turboccc.wikispaces.com/Extra_POI_Editor

Can gpx files be loaded/mixed on a garmin with csv files.

Yes you can have both gpx and csv files loaded to your gps. See http://www.poi-factory.com/node/6203 for more info.

Thanks Charles45 for the help
DeWayne Nuvi 660

I take the csv files I want alerts for and use the Extra Poi Loader to convert them to a gpx file.It has a setting when you go to edit then replace field.Under field name use down arrow to select proximity and in new field value put number of ft you want alert for then click replace all.This builds in the alert for each custom poi all at one time.This allows you to use the express mode instead of the manual mode for poiloader.

You can also open gpx files in Google Earth. This will put a flag at each point on the map where a specific point in that file is located. Kinda neat if you want to get the big picture of where all those points are.