Trump is scheduled to meet with British Prime Minister Theresa May and Queen Elizabeth II later this month.
The demonstrators plan to loft a large blimp-like balloon over the skies beside Westminster Palace, depicting a bronzed "Trump Baby" in diapers, clutching a mobile phone.
Its advice to USA citizens was to "keep a low profile" and "exercise caution if unexpectedly in the vicinity of large gatherings that may become violent".
Trump Baby, designed as a statement of protest as Trump visits the United Kingdom this weekend, was brought to life by a crowdfunding campaign, which exceeded its initial £5,000 (S$9,000) target so exponentially that there are now plans to take the balloon around the world, following - and taunting - the U.S. president wherever he goes.
Temporary signs indicate road closures around the USA ambassador's residence, where special fences have been erected prior to the US presidential visit at the end of the week, in Regent's Park in London, Britain, July 10, 2018.
He will spend just one night in the capital before going to Prime Minister Theresa May's country retreat Chequers in Buckinghamshire.
In this photo taken on Tuesday, July 10, 2018, children play basketball in the foreground as a six-meter high cartoon baby blimp of U.S. President Donald Trump stands inflated during a practice session in Bingfield Park, north London.
Trump angered May and many Britons by tweeting inflammatory and unverified videos made by Britain First, an anti-Muslim group whose leaders have been convicted of hate crimes, and by characterizing parts of London and other cities as no-go areas because of a purported Muslim-related crime wave.
"It's typical, but honestly Donald Trump's legacy will outlive any big orange balloon and the matters that will be discussed at Chequers and now in Brussels are much more important and will have a much longer effect than any day rally", she said.
Later, Trump will go to Windsor Castle for tea with the 92-year-old queen.
"There is no stronger alliance than that of our special relationship with the USA and there will be no alliance more important in the years ahead", May said in a statement.
The National Police Chiefs' Council said discussions were ongoing about "how the resource requirements of this massive operation will be met" but a spokesman said: "We are confident that forces will continue to maintain local policing services".
The security operation is estimated to cost between £8m and £10m and will put police under "unquestionable pressure", according to Police Federation chairman Simon Kempton, who said operations were likely to become "merely reactive" during the visit.
While Mr Johnson may now be a backbencher, Mr Trump said he hoped he would still see the former foreign minister - another blow to the fragile position of Mrs May.
In a frank exchange with Piers Morgan on Good Morning Britain, Mr Khan said: "My views are irrelevant".