Had tight 38 and 32 minute connections R/T to SGU from SAN this week but put faith in DL's operational excellence. While DL was punctual I didn't know about the bus terminals! What would have been a good experience turned out to be one that we will not repeat unless there is about an hour to connect as we had to run on the return to make the flight. By the time we boarded, of course the overhead bins were packed in our cabin (C+). Our flight to SGU on Monday was MX delayed so they kept us on a bus with no A/C and temps in the 80's (90's in the bus). After about 20 minutes they took us back to the terminal only to reboard us a few minutes later. Sitting on a bus for 20 minutes with broken A/C soured what would have been a great DL experience.