It is useful to be aware of the politics in this part of Italy (in fact, best not to discuss with Italian casually, unless you know them). The Trentino has changed hands between France, Austria and Italy over the centuries, reflected in the fact that the region is bilingual - German and Italian. However, many natives feel more strongly towards Austria than Italy, and speak German as their first language. As a visitor it is best to respect these differences, rather than question them; the Italian government gives extra money to accommodate both cultures, and the result, in my opinion, is very interesting and engaging.
Using public transport, I recommend the train to Malles Venosta, further up the River Adige valley. It is a scenic and enjoyable journey, and Malles offers medieval buildings, fine mountain views and cheaper restaurants and bars. The service to Bolzano is also worthwhile, and make sure to take the cable car to Oberbozen on the high ridge above the town, followed by a trip in the historic trams that traverse the ridge. If you enjoy walking, there are many signposted walks in this area.
Trento is also easily reached by train, where there are many historic attractions including the famous Duomo, and an excellent museum.
In winter Merano services the nearby ski resorts, especially Meran 2000 which is reached by cable car from Merano. If travelling from abroad, the most cost-effective airport to use is Verona, which offers direct service from a wide range of European airports, and some from beyond Europe.
I thoroughly recommend a visit to Merano, and you will return with your lungs full of fresh mountain air.