The technique to do this uses the fitBounds method after you've got a map with markers placed on it.
See http://stackoverflow.com/questions/10268033/google-maps-api-v3-method-fitbounds for some sample code to accomplish this.
Hope this helps,
It is my understanding that the zoom doesn't work (and thus not required) when using bounds.
Yes, once you're using bounds methods *after* markers are added this is true. Problem is zoom and center are required on map initialization. There's no way to skip around that requirement until after the map is loaded.
Here's a really clean explanation of the recommended order of operations: https://coderwall.com/p/hojgtq
Thanks Perren. That's helpful.