You should be able to pick up a free island map (which includes some town maps) at the airport.
Try the Cabildo de Tenerife website for places of interest and maps:-http://www.puntoinfo.idecnet.com/index.php?lang=2&s=1§ionID=80&ID=4234
Their Tenerife road map is particularly good.
There are many other sites from which you can obtain free maps, just do a Google search. In particular, enter, ldblquote Tenerife Tourist Information Guidedblquote .
There is a link on the home page of Losgigantes dot com (top right)to a site called Island Drives, which is promoting a car tour book for Tenerife which looks very interesting, if you are prepared to pay. I am not sure if the quoted cost includes postage to the UK. If anyone has bought and used the book I would be interested to know what they think of it.