Hello Purnima,

KCET is an annual exam that is conducted by the Karnataka Examinations Authority for admissions to various engineering, B.Pharm and Farm Science courses in various institutes of Karnataka.

Being from Mumbai, you are eligible to give the exam but won't be able to take admission in Government seats unless you have studies in schools of Karnataka for a minimum period of 7 years and have passed your class 10th and class 12th board examinations from schools in Karnataka. So, in my opinion it isn't worth giving KCET as you won't be getting admission in government colleges. 

For more details follow the below links:

https://www.careers360.com/exams/kcet

http://kea.kar.nic.in/cet2019/eligibility_clause_2019.pdf