When I left last August, we had around 600 in engineering, around 900 in product and engineering.
Engineering was mostly based in SF but with satellite offices in London and Hamburg. It looks like they were expanding in a large way into a Toronto office too.
Infrastructure was around a fifth of that total but included verticals like search and machine learning infrastructure.
Yelp turned off their last datacentre in early 2018 (IIRC) - and is entirely on AWS.