Valparai can be visited throughout the year. However, some falls are seasonal to winter.
From Coimbatore, reach Pollachi and then head towards Aliyar dam. There is a park and dam that can be enjoyed there. After aliyar dam, the ghat section starts. Within few KMs, you can reach the monkey falls. That is a seasonal falls. After that you will have a nice ghat section full of nature. After 500 meters altitude, tea estates start and the climate becomes excellant from then.
Balaji temple in Valparai is a good place to visit. It is a private temple and closed during noon timings. Please check the exact opening timings before you visit.