hi there!
coming from the region... from the swiss part... very nice either!
My personal advice:
you take the direct train to Stresa, you have a day visit there, you take to boat to Locarno the day after.... May is sunny and already warm!
once in Locarno, you can hire a car, (I advice to do it!) you can then go to Ascona (just great) and then visit the Cetrum of Monti della Verità (more and more internationally recognized for place of international conferences on meditaiton, peace, and political one) where you can have a visit in the real japanese House of Tea! (also there is a local green tea producer where japanese Tea Masters comes once a year to taste and value it).
then the great (if you like nature) valle Maggia and Valle Verzasca (you can do a thrilling bunjing jumping... the same jump made by 007 in Goldeneye)!
There you can try all kind of traditional South Alps dishes! the Alpine cheese!
YOu can try some wine caves.... you will find some great surprises!
Then within 15km by Locarno, you can visit the Unesco-protected castles! and going to the South of Ticino (40 min.)
to the Mount San Giorgio, another Unesco protected site with prehistoric animals discovered....
drop me a mail if you wanna have more information on specific queries ok?
here a hint...
http://www.ascona-locarno.com/default.jsp
this is the touristic information centre, surely helpful.
have a nice trip and have a good evening :-)
E.