Travelling alone is a great way to meet other people and you can make sure you get to see all the sights you want :-)
Companies like STA, BusAbout, Contiki all do travel tours, bus tours etc. where you can meet other travellers so this could be a good option.
I would recommend staying in hostels and checking out any free tours, pub crawls etc as this can be a great way to meet other people.
Hope this helps!