if I get 300 in neet 2020 can I get any medical clg in all India qota below 5L fees?

You haven't mentioned your Category. Nevertheless, Under All India Quota, All the 15% of All India Quota Seats except for Jammu and Kashmir, 100% Seats at Deemed and Central Universities, IP Quota seats in ESIC Colleges, Seats at AFMC, AIIMS and JIPMER  are filled by DGHS. If you look at the line up of these Institutions that conduct admissions through All India Quota, they are AIIMS, JIPMER, AFMC, etc. And a seat in these Colleges with a score of 300 even if you belong to Reserved Categories is difficult. There are Management Quota seats in Deemed Universities but their fees is not below 20 lakhs atleast. So unfortunately there is no College that might give you an admission with a score of 300 within a fee structure of 5 lakhs.