While Colossus Blvd is not a required area, it does teach you about dueling more than one creature at a time. You may find if you skip this area, that you're not quite strong enough for Krokotopia.
I would suggest doing it for two reasons, 1) it prepares you for the two on one battles you will have to encounter from this point forward and 2) It gives you the Experience points that you should have for Krokotopia. You don't HAVE to have these points but it's better for you if you do.
