A minor controversy regarding advertised and allowed time controls has broken out on a chess mailing list I subscribe to. A one-day tournament scheduled for tomorrow advertises specifically as five rounds of G/30, and a member of the mailing list has claimed that any player can therefore demand G/30 (as opposed to G/25 d5), regardless of their opponent's wishes. The last time I played in this particular tournament, I asked the organizer if I could insist upon G/25 d5, and he said that it's my right to do so under USCF rules. Is this true, or does the fact that the tournament listing states G/30 (and doesn't mention an alternate time control) mean that I should actually be forfeited if I request a delay and my opponent refuses?
You don't have grounds to demand the time control you like. In practice I suppose that if your opponent agrees, you could get away with using whatever time control you both want as long as the game finishes on time, which is the main point the organizers care about.
One thing that the USCF rules do cover is what to do if the stipulated time control has a delay or increment and the only available clock doesn't support it. In that case the "base time" should be used instead.
However: did the advertisement say just say "G/30", or was it "G/30 d0"? Because according to the USCF, "If the organizer fails to specify an increment or delay time in the time control (which may be zero to indicate no increment or delay), the minimum recommended delay specified in rule 5E shall apply." The minimum recommended delay for 30 minutes is 5 seconds, so the way I read that, if it was advertised only as "G/30", you'd have grounds to demand G/30 d5.
You are close, but not quite right.
I just spoke with a friend of mine, who has been a tournament director for over 40 years, USCF Senior TD Henry L. Terrie III (Hal Terrie). He told me that when you post a USCF tournament, you need to specify the delay, or it is assumed to be 5 seconds.
So, while you cannot demand G/25 d5, you can demand G/30 d5 since it was not specified. That is the only variance you can demand.
5B2: Advanced publicity time controls need to contain both the base time control and the delay/increment.
5E2: Organizer fails to specify increment or delay: Subrule added to new rule 5E with wording addressing the lack of a specified increment or delay. If the organizer fails to specify an increment or delay time in the time control (which may be zero to indicate no increment or delay), the minimum recommended delay specified in rule 5E shall apply.
It is in the PDF download here for "Chapters 1, 2, and 11 Combined".
If the tournament advance publicity specifies G/30 with no delay, then that is the time control. There is nothing in the USCF rulebook that would give you or your opponent either grounds to request a different time control, nor discretion to agree to a different time control. Per USCF rule 5B1c and 5B2, the time control really should appear in the tournament advance publicity as "G/30 d/0", but in practice the absence of "d/0" is generally understood to mean "no delay". (EDIT: However, itub's answer is correct, rule 5E2 does specify that if the absence of delay or increment is not explicitly stated, the minimum recommended delay "shall apply" - note that "shall" indicates that there is no discretion, it is just a fact... - which would mean that the time control that should actually be played should be G/30 d/5.)