When faced with this decision, I bought a Tamron 19-35mm AF zoom. Slower, bulkier, and I guess inferior image quality to the primes (but not bad), but it meant I could play around until I decided which wide focal length suited me best. From memory it cost less than 50 inc. shipping from KEH to the UK. I could probably have sold it for a similar amount in the UK, but in the end kept it and bought a Nikkor 24/2.8 as well.
Ian