You want to go to places that wouldn't be too noticeable. Like if there is a highs chool by either of your houses.. go there and just chill out where nobody can see you. Or in the woods, on playgrounds at night, in the car, if you go in the mall you might be able to sneak in a dressing room together and do it there, or just tell your parents to lighten up because if you are 18.. they have no say in what you do and tell them that if you are not even having sex they shouldn't care.. at all.
Good Luck, believe it or not.. your parents are trying to help you out. It seems like they are just being rude and that kind of thing but seriously they don't want you to get pregnant or anything.
Totally with ya here, I'm 18 too and he can't be @ my house, and vise versa.
What we do is, chill in his car and go to a neighborhood, or their is a park right across the street from my house, and late at night we go their because we know that no kids are gunna be there. Don't go to a major big park, do you have any little parks that are like in a neighborhood that you might know of? hopefully this helps.
I almost always made out in the car... We'd go to new subdivisions or developments where nobody was at night. Behind strip malls (look for security cameras... you wouldn't want to give some security guard a show). Way in the back of the mall parking lot. Friends houses. You can always find places to park if you have a car :)
Sometimes the most obvious places nobody will look. But don't rush it, rather look forward to all the freedom when you are married otherwise you will just get tired of it and it could become a mundane ritual if you do it all when you are still young. Let it come naturally and let it be a journey, and not a race to finish as fast as possible, otherwise you'll never like it anymore in the future, cause of "been there done that". You'll be 50 before you are 30. But anyway let it come with opportunity, like walking along the road and going somewhere quietly.
Your car in a parking lot, the movie theater, etc...