have experienced myself. 1hour or more was the time taken to cross during the evenings. may not be true in present days. but the traffic in the perumbavur-angamaly stretch is multifold compared to earlier times.
the route towards perumbavoor are all in bad conditions. yesterday, I passed through Vengola to reach Marampally, there was works going on and wasted some 10-15 minutes at Vengola Junction due to traffic piling up in all directions. also, Pukkattupady-Perumbavoor road will be almost always in bad condition with Taurus/Tippers and long distance buses driven badly. in general every road in between perumbavoor and NH 49(south) is bad. including infopark karimugal road. kakkanad-kizhakkambalam road etc.
you can come to Kakkanad through Seaport-Airport road then Kalamassery-Aluva-Athani-Airport-Mattor_Kalady.
is the straight option to reach from Vaikom.
from Vaikom, another option may be to take Thrippunithura-seaport airport road to reach HMT and take right turn(ask for the route to choondy) to NAD road
to reach Choondy in Aluva-Vazhakulam-Perumbavoor private bus road which is rubberized highway(macadam laid) in good condition. at Vazhakulam( ask for Marampally road). the road to Marampally is narrow but not in very bad condition and it is some 3kms or so.
take left at Vazhakkulam and reach Marampally(KSRTC route from Perumbavur to Aluva). from Marampally take a right turn and go northwards for Sri Sankara Bridge-Kanjoor-Kalady.
this will be a good option considering few stretchs are narrow like Vazhakulam-Marampally road and Marampally-Kaladi. always stop and ask for direction while going through circuit roads like shown in Google map as one can easily lost way if not asked at junctions: http://goo.gl/maps/rhe5n