The only time I’ve had issue with the bus system at CSR is the day of the marathon, but transportation in general that day is a logistical nightmare. If you want to make sure you get on the bus (ie, it’s super crowded during your visit for some reason), walk to Casitas as that’s the first stop unless things have changed recently. You’ll have to complete the loop before taking off for the park, but at least you’ll be on the bus.