VANCOUVER -- Optimism mixed with thick clouds of pot smoke in downtown Vancouver last year as tens of thousands of people gathered for the annual "4-20" marijuana legalization rally under a massive banner featuring Justin Trudeau's face on a rolling paper.

But this year, the event's chief organizer, Jodie Emery, says "inaction" by the newly elected federal Liberals makes the protest "more necessary than ever."

"Last summer I was joking I'm going to be out of work as an activist because we don't have debates anymore, there's no one fighting to keep it illegal," said Emery, who is the wife of "Prince of Pot" Marc Emery. "But fast forward to today and the mood is different."

Trudeau has pledged to legalize pot and struck a task force to hammer out legislation, but Emery said change could be months or years away.

Vancouver, meanwhile, is preparing to shutter over 100 marijuana dispensaries by end of month as it regulates the sale of pot.

But while Emery worries about progress, other proponents of legalization argue Emery and her allies are sabotaging their cause.

"They're doing themselves a disservice," said Dr. Patricia Daly, chief medical officer with Vancouver Coastal Health.

"They are not just protesting in favour of legalization. They are actually selling the product in a very unregulated way and it's exactly those activities that make us advocate for a strong regulatory approach."

Preparation was underway Tuesday on the eve of this year's event, which has been moved to a beach after mostly being held outside Vancouver's art gallery since 1995.

More than 100 people -- the youngest aged 15 -- went to hospital last year complaining of symptoms ranging from upset stomachs to acute anxiety and psychosis, Daly said. Sixty-three people were treated, and 75 per cent of them had consumed edible marijuana products, she said, noting pot in food presents the greatest risks.

The city issued a statement saying the protest is unsanctioned and unlicensed, but it recognizes the public's right to peaceful assembly and lawful protest.

More than $92,000 was spent by the city last year managing safety and cleanup, including $52,000 on additional police officers.

Organizers agreed this year to move about two kilometres away to the beach, where vendors will sell exotic strains of pot, paraphernalia and edible marijuana products.

City staff, police, fire and rescue, and the Park Board have worked with organizers on a public safety plan, and volunteers will distribute free "4-20" guidebooks, a new addition featuring a site map, health advice for safe marijuana use and political messages.

Emery said the grassroots event remains non-profit, but organizers have raised $100,000 this year to cover costs of fencing, portable toilets, first-aid booths, security staff, a stage, garbage bins and containers for used joints.

Organizers will also use radios to communicate with police, fire and rescue personnel, as well as the ambulance service, while reminding participants the event is alcohol-free, Emery said.

Vancouver's board of education distributed a fact sheet to parents recommending conversations with adolescents about the risks of marijuana. It suggests parents plan alternate activities "that are super fun," such as taking teenagers bungee jumping.

Emery said she is frustrated the city has not sanctioned the event and will close public bathrooms around the beach.

"A lot of people will attend to celebrate, because everyone does feel marijuana will be legal," she said. "But we have to explain it's not legal yet and we still need to push the government to stop arresting citizens."

Nearby St. Paul's Hospital is mobilizing extra emergency room staff, Daly said. Public health officers will advise vendors not to sell to minors.

"There is no other mass gathering that results in dozens of people showing up at a hospital emergency department," she said. "The only other event comparable was the Stanley Cup riot."