Sorry to hear of your predicament. You are in a tough situation. A couple of quick points:
1. As a previous poster noted, it is imperative that your friend re-enter the US in an appropriate status. Lying to the immigration officer on re-entry can have extremely dire consequences, up to a permanent bar on re-entry into the US. Not a risk worth taking IMHO. The better course of action is probably to cancel the trip.
2. The time it takes to get a tourist visa varies greatly by the specific consular post. See this State Department website for the specific wait time at the consulate nearest your friend's (foreign) home:
http://travel.state.gov/visa/temp/wait/tempvisitors_wait.php
Please note that unless there are compelling reasons for it to be otherwise, consulates will only consider visa applicants from the relevant locality. Within the last couple of months a friend of mine from the UK had to cancel a US trip because he could not get a visa in time. (He is ineligible for the visa waiver program because of an old DUI). Wait times in London were about two months and when he explored going to Copenhagen (wait time 1 day) to get the visa quickly, he was told by the US embassy that that would not be possible.
3. If you are planning on living in the US after you get married, you need to apply for a fiance visa at any rate. These take time, so may want to look into applying now.
4. Contrary to what a previous poster suggested, I am not sure that looking for another job is a viable option. A new employer would have to apply for a new H1b for your friend since the visa is job and employer specific. H1bs are over subscribed every year and each year's allocation is used up literally within a day or two of the beginning of the fiscal year (October, I believe). Thus even if your friend found a job, it would be months before he could start.
4. Finally there is the issue of how long your friend can stay in the US now that he is out-of-status. I don't know the answer to this question but I have a dim recollection that an immigration lawyer told a friend of mine in the same position twelve years ago that he had a month from the end of the job to exit the US. For what it is worth, he left within that time frame and then lived outside the US for a number of years before securing his green card.
Best of luck
