Yes, you can file RTI application in Telugu.
Section 6 (1) in The Right To Information Act, 2005:
(1) A person, who desires to obtain any information under this Act, shall make a request in writing or through electronic means in English or Hindi in the official language of the area in which the application is being made, accompanying such fee as may be prescribed, to—
(a) the Central Public Information Officer or State Public Information Officer, as the case may be, of the concerned public authority;
(b) the Central Assistant Public Information Officer or State Assistant Public Information Officer, as the case may be, specifying the particulars of the information sought by him or her: Provided that where such request cannot be made in writing, the Central Public Information Officer or State Public Information Officer, as the case may be, shall render all reasonable assistance to the person making the request orally to reduce the same in writing.
To file RTI application please refer https://onlinerti.com/apply or mail us at firstname.lastname@example.org