I've spent three summers in DE. I really, really had a great time. I didn't stay at Bethany, I stayed in Rehoboth Beach but I've been in Bethany Beach many, many times since it is really close. It depends on what time of te year you will go there. During the summer time it is really fun, there are many people and lots of restaurants and bars. I don'r recommend you to go there during the winter-there isn't much to do. The beach areas are pretty much emply (besides on Christmas and New Year), most of the bars close-especially in January-almost nothing is opened.
other than that it is a great place to visit, especially if you go there with goo friends. You will have a blast. The cheapest way to get there (if you don't live somewhere around) is to fly to DC or NYC or Philly and then take a train or a bus to DE. For cheap flights I recommend you this website: www.expedia.no. If you are with some friends you should definitely take a cab from DC-its about the same price as the bus if you share it.