Assalamu Alaikum wa rahmatallah wa barakatu
I am growing a beard. But it is almost invisible unless you look really close.
like the fuzz my bro is trying to grow now

lol mashallah..inshallah it'll grow into a full length beard ekhi
I just wanted to say something, I have a very low voice when I talk, because I'm quiet and shy naturally, so when I say my salaams a lot of times I'd raise it so that people will hear me and they still don't, othertimes they might reply without nifis (feeling) or sometimes its just not happening for me all together...anyways someone told me that when you say your salams with true intentions and it's not returned, then it is to Allah subhana wa ta'ala. So just keep that in mind. If the person doesn't reply because they were skeptical in providing dawah for a bro that knows an islamic phrase or two, then its their loss..your intentions always return to Allah.
Like other people have already said, say the full salaam inshallah. When you talk to someone say "inshallah, alhemdulilah, mashallah, allahu akbar" little things like that will get you noticed inshallah.
e.g.
You: Assalamu Alaikum Wa Rahmatallah wa Barakatu ('ekhi' could be preferable here to show you know a bit more than just the salaam part)
Brother:

oh: :mmokay:
You: Inshallah you are doing well today ekhi
Brother:

oh: Walaikum assalam wa rahmatallah wa barakatu, yes alhemdulilah, I'm fine..
end
It might not go exactly like that, but you get my drift
and its not cuz you're white, its cuz it's their problem. Even if they aren't sure they should at least reply with "wa iyak", that's sunnah. Being Muslims, our first reaction is to be overly protective of our religion when we think its being ridiculed especially when we see a nonmuslim (or someone who looks like a nonmuslim) doing it. Perhaps too many, because of your age, its difficult for them to percieve that you are a Muslim, allahu A'lem. It's still no excuse for them.
fi aman Allah
w'salaam