Girls 16+, is it a good idea to not approach attractive girls because I want to wait until marriage for sex?

I noticed recently in two different instances today some attractive girls being talk to by multiple guys. One of them I didn't have that chance to talk to and the other I didn't catch her fast enough to talk to her (or I would've been interrupting her workout). Would it be smart to approach girls that are more modest with looks than very attractive girls? Most very attractive girls are social butterflys so it's safe to assume they may be sexual active. I want to wait until marriage for sex (18 y/o, 19 in 2 weeks) because it's in my Christian beliefs. Is my rationale correct or should I go for it? Opinions/Suggestions?