I'm a late bloomer, who's turning 21 in a couple of weeks and yet have had my sexual debut. However, I don't "plan" on saving myself. To me, marriage is just a pointless ceremony, made to give people the impression that you're sealing some sort of pact that will make you and your partner together forever... Just saying you don't want to leave the person would work for me personally, though I might propose to whoever manage to melt my heart and stay with me for some time, not that I have anyone... But no, I personally don't mind pre-marital sex.
I mean, imagine marrying someone and then you realize that night that your "lawfully wedded" wife/husband is a complete bother to have sex with?
Bad sex can lead to bad marriage. You want to risk that by being abstinent? In that case don't complain if you find out you're not sexually compatible with whoever you marry : /