When I began working with my teacher, I had a fair amount of technique and some music knowledge, but apparently understanding theory and knowing how a scale is made is different from sightreading.
We focused on reading for about four months before we began working on jazz. I mean, it was stuff that was way, way beneath my playing, technique-wise. It was hard for me to believe, while I was struggling with it, how bad I was at it! It was like I had never been that bad at anything before.
About a year and a half later I am able to read all kinds of rhythms in any key. My reading practice these days is mostly Jamerson material w/ Simandl. Because some of the rhythms are complicated for me, I still begin working on a song at 60-70bpm, but Motown sure beats "Michael Row Your Boat Ashore" or whatever.
Being able to go through a book like Bert Ligon's "Linear Harmony" and play the licks at a reasonable speed while reading about the analysis is so much fun by itself that it doesn't occur to me that I'm trying to be a great jazz player and I still have a long, long way to go.
Besides, most people will learn better if they have a variety of representations of the material they are trying to learn. The aural expression of music is the most critical, of course, but seeing the notes on the page sure did help me start to feel the groove through the measure.
PS, learn to read treble clef. It does get a little confusing, but in this world, unless you're looking at an educational bass product, you're probably going to be seeing mostly treble clef. I think this is much easier to do all at once, like you would with piano.