This is a tough question, depending on your state law and most state law at 18 you are a legal Adult on thr oher hand you live withyour parents
i lived with mine til my early 20's and one thing they instilled in me, was that no matter what they loved me, but they also said, do as you wish, go where you wish be with you you wish but if you get into trouble, busted ect, DO NOT CALL US to bail you out, either fromjsil or the trouble itself
I leanred to be carefull with what i did, who i was with andi was brough up in what i would term a liberal family
There was little as an adutl i was not allowed to do ib or out of the house
but my dad always reminded me "I do not care if you are 15, 18 or 25, if you remain in the house with your mom and me livinghere, there are rules to be followed, you do not have to like therules but you have to follow them"
I leanred over theyears as an adult even at 18, that some thing i did that wee legal, fun ect my parents did not like, but they also respected thefact that aside from living with them, that i was an adult

i wouls try if you can to sit down with your parents and be honest, tell them you know how they feel you respect that, you may not agree but you respect that, that alone is worh thetalk, be honest and tell them how you fell and find out exaclty why they feel like they do, then if you can take it 1 step further and asked how they did things when they were your age, did they do things their parents thought were sinful and if so what did they do
give it time, repsct trheir feelings, but even as a 19 year old adult, youstil live undr their room, they feed you give you place to sleep at night, so you also need to respectthat
i hope this bit of advice helps you a little and good luck
Remember bakc when they were teens not knowing how old they were they may have loved Frank Sinatra as a singer, their parents may not have, in thr 50's thesame thing with Elvis some kids loved him their parents did not, as time goes on and has gone on gnenerations like different things and they need to also remember that 2008 is different then say 1960 or 1970 to 2 different gnenerations, 2 different set of belifs and likes an dislikes when ou get married and have kids time will be that they will do what you are not happy with, just like yourt parents are now