Actually, I think there is real value to separating the rhythmic considerations form the melodic ones. yes both are valuable, but rhythm , for me is far and away the harder of the two. Drum music is great for learning rhythm.
Reading, writing, hearing and transcribing all cross-feed each other as skills: learn to write baselines you come up with, and play rhythms you come across.
Start simple and work your way up, or rather: start with whole notes and half notes(and their rests) , then work your way into more detailed quarters and eights.
don't expect to be notating 16thnote funk rhythms before you can hear the difference between an dotted quarter note and a quarter note
good exercises[Invalid or Expired Link Removed].
For me, latin music was very helpful for rhythm reading because it's very syncopated but rarely more detailed than eighth notes and rests.