From a home users standpoint, port 80 outbound is open - it has to be because as you said, standard HTTP runs on port 80. Port 80 inbound is what is blocked by some ISP's here in the USA. They do the same for port 25 (SMTP - Email) to prevent people from running mail servers in their home. It's only some ISP's, not all.
If your program will be strictly used in SA, then port 80 may be fine for you. If this is going to be an international application, port 80 may not work for you.