Nice to have a positive interview. My 2 cents.

Don't postpone it. On the contrary, be proactive on this interview. Interviewers don't like being postponed unless the candidates have emergencies, or they are at the top of the field and are really hard to recruit.

Also, a bird in the hands is worth two in the bush. It is worth more than two, actually, especially at such an economy.

Furthermore, the periods from the initial interview to the final offer vary dramatically among companies. So you don't really know which offer will come first. In general, it takes longer for big companies. AT&T is not well-known for their efficiency.

You can always resign if you have a better offer, if the employment is at will for both parties.

Good luck.