I interviewed for a backend/infra position.
Spoke to an engineer at a career fair and got a coding challenge a few days later(also attended a tech talk on campus and spoke with the same engineer there). From there I did a phone screen on Skype. The final round was 2 back to back Skype calls. I received a phone call after a few weeks with an offer. The whole process took about 2 months and 3 days from coding challenge to offer letter.
Overall I was very upset with the recruitment process from Yelp and expected much more from the company. It took 5 weeks to schedule my first interview(I sent 4 followup emails during this time and had to give more availability because they couldnt schedule in the 4 weeks I originally provided). By the time it came to my first interview I had to schedule them around my finals week because the process had been drawn out so long. The process took 61 days from coding challenge to offer.
I was able to complete a coding challenge, 3 interviews, and receive an offer call in the same timeline for a different company than it took to complete my first interview with Yelp from time of completing the coding challenge.
From my experience talking to other students at my school several other students felt the same frustration as I did when dealing with the recruiter. A common advice from several others was to just contact another recruiter to get an interview scheduled.