On page 19, Elwood compliments Kelly, telling her, "You really are very lovely." Kelly replies by thanking Elwood for the compliment and also remarks, "Some people don't seem to think so." When Elwood says, "Some people are blind," what he ostensibly means is that some people are blind to Kelly's...
loveliness. In other words, he is simply continuing the compliment, by reassuring Kelly that she is indeed lovely even if other people can't see it. There is also, of course, an ironic secondary meaning to Elwood's line here, as people in his life are blind to his friend,Harvey, the six-foot, white, anthropomorphic rabbit. They are also, in a figurative sense, blind to the world of the imagination that Harvey symbolizes.
On page 49, when Elwood says to the doctor that he "wrestled with reality for forty years, and (is) happy to state that (he) finally won out over it," he means that reality is, or at least can be, and has been for him, an oppressive and antagonistic prospect. Reality is about climbing the social ladder (his sister, Veta, for example, lives in this reality) and accruing materialistic gains. Reality in the sense that most adults know it is not about being pleasant, getting on with everyone and indulging the imagination. And this is why Elwood is happy to have finally escaped the reality to which the doctor is referring.
Elwood later says to the doctor that he had "such hopes" for the name Harvey precisely because he had never known anyone with that name before. In other words, the name Harvey didn't come with any connotations, good or bad, owing to its association with other people named Harvey. The white rabbit could, therefore, exist as a completely independent personality, a blank slate upon which it could write its own character.