According to the Baltimore Sun, at least one of the race's former competitors, along with others, are not pleased with Armstrong's presence because in order to host him, the race had to be de-sanctioned by USA Triathlon, meaning results from the race will not count toward pro athletes' rankings.
Because Armstrong has been banned for life from competing in sports governed by organizations that adhere to the World Anti-Doping Code, he cannot compete in any USA Triathlon-sanctioned events.
However, the decision to allow Armstrong to compete has increased participation in the event overall, according to event organizer Brian Satola, who is chief operating officer of the Ulman Cancer Fund for Young Adults, which receives the proceeds from the race.
"We've had over 200 new registrants since [Armstrong's] announcement and only two people have asked for refunds," said Satola.
Satola said his organization was excited to have Armstrong participate in the Oct. 7 race.
"When we can have an event that from day one is focused on the cancer fight, and then you have arguably the most recognized cancer survivor to attend your event, it has been overwhelming," said Satola.
Despite not being sanctioned, a $25,000 purse will be split among the top six finishers, with first place getting $4,500, according to the event's website.
Armstrong was banned from all USADA (U.S. Anti-Doping Agency) sanctioned races after he decided not to continue fighting doping allegations levied against him in August, although he stated the allegations were a "witch-hunt."
Afterwards, USADA stripped Armstrong of his seven Tour de France titles.
Most recently, Armstrong competed in a non-sanctioned marathon in Steamboat Springs, CO. He won the event with a time of 3 hours, 18 minutes and 10 seconds, according to the Denver Post.
Satola said the Ulman Cancer Fund hopes to raise about $200,000 from the race, which would be a record for the 3-year-old event. Registration for the event is open until Oct. 5, said Satola.
"It's going to raise money, raise awareness and we're going to help people," said Satola.