Since google trends require you to login, can I still use an IP rotator such as crawlera to download the csv files? If so, is there any example code with python (i.e python + crawlera to download files on google). 
Thanks in advance.
No one is going to write code for you.
But I can leave some comments because I have been using Crawlera proxies for the past few months.
With crawlera you can scrape Google Trends with new IP each time, or even you can use a same IP each time(its called session management in crawlera).
You can send a header 'X-Crawlera-Session':'create' along with your request and Crawlera on their end will create a session, and in response, they will return 'X-Crawlera-Session': ['123123123'] ... And if you think that you are not blocked from Google, 
You can send 'X-Crawlera-Session': '123123123' with each of your request so Crawlera will use same IP each time.
Is it possible to use a proxy rotator such as crawlera with google trends?