If you're bringing a coach to St Ives, the best way would be to take the 'Coach road.' When you leave the A30 and drive past Wyevale Garden Centre follow signs that read 'St Ives (day visitors)' which are on brown signs. This route will take you behind Carbis Bay, a residential area and avoid congested areas and narrow roads. Follow this road until you meet the B3311 and turn right which will take you to St Ives (2miles) through Halsetown (1/2 mile). At the end of this road, another junction, turn right on to B3306 which will head towards St Ives (1 mile).
There is a free coach park opposite the Leach Pottery (TR26 2HE) alternatively you can park in the Cornwall Council Coach Park located within Trenwith Car Park (TR26 1DD) which is where the Leisure Centre is. From both of these locations there is a shuttle bus running down to Royal Square. The map above highlights several possible routes, however the best route is as previously explained, which avoids Lelant, Carbis Bay, Cripplease and Penderleath.
There is a park and ride bus service operating from the Trenwith Car Park to Royal Square.
If you are using a variety of Cornwall Council Coach Parks then why not obtain a rover coach ticket?