Where I am from in the Midwest, weddings always have a table set up in the reception hall for gifts and cards. EVERYONE brings their gifts to the reception. Then, the brides family customarily loads it all up after and takes it to it's final destination.
Good advice from others also:
1. only bring a guest if the invite says you can
2. Dress appropriately for the type of couple and place you will be. (If a backyard bbq, jeans are probably o.k. If at a country club, formal attire is in order)
PLEASE, if you want people to dress informally, note it somewhere in the directions or something!
My husband and I were recently invited to a wedding reception (the wedding was held in another state). My husband knows the people through work and never could get a coherent answer about appropriate attire. All I knew was "not formal". I wore nice, light dress pants, blouse and heels.
The party was at a park shelter. Most guests wore shorts, and t-shirts. I felt foolish, and that is not a nice way to treat your guests!