Hanging out with guys in the summer time is great. Here are some tips on how to get started.

[edit] Steps

Get out there. Make sure you know the guys you want to hang out with. Send them a text message or say hi if you ever get the chance.
Get noticed. Wear a cute outfit, but nothing too fancy. If you have a pet or a younger brother or sister (like really little) and they are very cute, take them outside when the guys are outside (ahh coincidence!). Let your little munchkin run over there. Most guys will notice them first then you come over and they will notice you. Casually start a conversation. Ask how their summer's been, whatever.
Get involved. Ask if they want to play ding dong ditch or some other fun thing. If you have some girlfriends, invite them over so you can all hang out (at first). Sooner or later you'll just be able to go over there and hang out with the guys.

[edit] Tips

Look nice, but don't look like your trying too hard. Guys hate that.
If you're nervous, have your girlfriends over and go on a walk. If one of you is daring, go down and say hey to the guys.