Assuming it has a micro SD card, you can download a map tile to the card from here:
http://garmin.openstreetmap.nl/
There is a tile for Tenerife.
Generally, the base map supplied with a Garmin is poor, but you can load a map (*.img fle) onto the SD card and the GPS uses that map file.
Getting it all to work can be a bit of a faff, but there is advice on here and elsewhere. I use an eTrex Legend HCx with a basemap from the link - there are several versions available, with different colours, themes etc. Some have contours too.
You do
not need to pay for mapping to go on your GPS.
See here too.
http://www.aukadia.net/gps/lwg_32.htm
Do not assume that all you have to do is load a file and it will work - Garmin is not like that - but an hour or 2 of research for your device will bring huge benefits.
