부를래요 is correct. Similarly, it would be 빠를래요 and 모를래요, but this ending is never/rarely used for adjectives like 빠르다. 모를래요 is also very uncommon, but it exists. 부르다, 빠르다, 모르다 do irregular conjugation for - 아/어 (불러요, not 부르어요 or 부러요), but it's regular for the -ㄹ래요 and other endings.