I went to Aruba alone on the front end of a trip a few years ago. I took the bus to get around and when my husband arrived we rented a car. He likes to go, go, go and I like to be a beach bum mostly.
Aruba is a place where you will find a lot of opportunity to meet people and strike up conversations. I really didn't feel lonely at all until late a night when I was back in my room and then I really missed my family because I didn't have a cell phone to keep in contact with them.
You will have a great time!!