You can take a bus from Porthtowan to Newquay via St Agnes, Church in around 1 h 25 min.
How to get from Porthtowan to Newquay
From Porthtowan, Beach Road line 315 bus to St Agnes, Church then line 87 bus to Trenance, Hilgrove Road. 1 h 25 min £5. From Porthtowan, Beach Road line 304 bus to Truro, Bus Station then line 93 bus to Newquay, Tolcarne Beach. 1 h 50 min £7. From Porthtowan taxi to Newquay. 23 min £69. From Porthtowan drive to Newquay. 23 min £2.