How will I live in Kerela without knowing Malayalam?

Not knowing Malayalam is not an issue in Kerala. Most Malayalies are multi linguists.

1.MIGRANT LABORERS.

The population is almost 10 % of the the native population in Kerala.

There are over 25 lakh(2.5 million) domestic migrant labourers in KERALA from other states of India, as well as from Bangladesh and Nepal , in 2016 this figure stood over 40 lakhs (4 million) with an annual arrival rate of 2.35 lakhs with a sum of Rs 25,000 crores going outside the state each year as wages to the migrant workers.

We can see them in shops, hotels, petrol pumps and almost all manual labor. So malayalies interact with them daily the local population can understand HIndi.

2.NRI’s

Around 3,000,000 Keralites(30 lakh) are working abroad, mainly in Persian Gulf; to where migration started with the Gulf Boom. The Kerala Economy is therefore largely dependent on trade in services and resulted remittances.

In 2012, the state was the highest receiver of overall remittances to India which stood at Rs.49,965 Crore (31.2% of the State's GDP), followed by Tamil Nadu, Punjab and Uttar Pradesh.

So NRI’s and ex-NRI’s can understand Hindi/ English making them polyglots.

3. EXPOSURE

Most youth in the state have experience of living outside Kerala.Either for higher studies(mostly in Karnataka and Tamilnadu) or for job(lack of industries). On average a Malayali youth have at least 3–4 years experience of living outside the state.

4. School curriculum

In schools(Government Malayalam medium) we have to learn Hindi and English from 5th standard(5th to 10th;11 & 12 can opt either Hindi or Malayalam). The 93.91% literacy rate is the highest in India.