Helguson swept the ball home from six yards on 52 minutes after Stoke had had the better of the first half.
Promising teenager Ashley Young almost extended Watford's lead when his shot fizzed narrowly wide.
Watford keeper Alec Chamberlain was forced to save David Brammer's header, but the visitors then comfortably held on for victory.
Stoke boss Tony Pulis:
"I hope it is someone who is connected locally and I hope a sale
happens fast," said Pulis on any possible new buyers for the club.
"If it doesn't we could be in danger of missing out on players who could take this club forward."
Stoke: Simonsen, Henry, Duberry, Taggart, Clarke (Halls 67), Greenacre, Brammer, Russell, Neal (Ricketts 76), Noel-Williams, Jones (Paterson 56).
Subs Not Used: de Goey, Buxton.
Watford: Chamberlain, Doyley, DeMerit (Cox 74), Cullip, Chambers, Young, Mahon (Bangura 30), Blizzard, Bouazza (McNamee 86), Helguson, Dyer.
Subs Not Used: Osborne, Kirk.
Goals: Helguson 51.
Ref: M Atkinson (W Yorkshire).