Mercedes' triple world champion Lewis Hamilton told reporters at the Bahrain Grand Prix on Thursday that it was a "pretty cool" move.
"I wouldn't miss out any of the races in Formula One," he added, although the Briton did express a desire to ride a MotoGP bike and race in NASCAR one day.
Alonso's Belgian rookie team mate Stoffel Vandoorne joked that he had decided to enter the Spa 24 Hours sportscar race on home soil instead of the Hungarian Grand Prix.
Mexican Sergio Perez said there was no question about where to race as far as he was concerned.
"I wouldn't miss Monaco to go to Indianapolis," he told Reuters. "Monaco for me is the most special weekend of the season, especially now that we have new cars, more loads, faster through the corners. I am so much looking forward to it.
"But at the same time I think it's a great challenge for Fernando."
Renault's Nico Hulkenberg, a Le Mans winner when that sportscar race did not clash with anything, said his situation had been completely different to Alonso's at McLaren.
"I would have never done it if I had to miss a race, especially Monaco," he told reporters. "Quite a big decision, big news obviously... I am a bit surprised like everybody about this situation."
Read the full article on eurosport.co.uk: Monaco comes first for Alonso's F1 rivals