Can myBritish husband travel to the USA while his visa is being processed?

Can my British husband travel to the USA while his Visa to live in the USA is being processed?  Also how long does it generally take to get the green card after applying.

Any help is appreciated.

He can travel to visit the USA while his visa is being processed. He can't enter with the intention of permanent settlement until he gets the visa in his passport. He will have to travel back to the UK for his visa interview and wait until his passport is returned to him -- a few days, usually -- before entering with the intention to settle.

For example, we made our application in August, then went to the US in September after attending the medical exam & submitting the paperwork stating we were ready to be scheduled for an interview. DH was granted entry on the VWP. He then had to fly back to the UK in January for the visa interview to get his visa. From September to January he could not work and was just in the US as a visitor.

So yes, it's possible -- just expensive and inconvenient.

Thank you for this. Really helpful.  We did not know if we would be able to take a vacation to the USA while his green card is being processed.  We aren't actually going to move until his card is finalized. 

We travelled to the US for a vacation and when we returned DH has his interview. We moved 6 months later. It was no problem at immigration. Have a great trip!