Should I file for Writ of Mandamus if my I-526 is pending for two years?

You can file, but I do not know what the chances for success are, since their posted processing times are so ridiculous. It is a good idea though perhaps to file as a class action.

You are eligible to file a mandamus action since the delay caused by USCIS is unreasonable. You should consult with an experienced immigration attorney who has successful experience in mandamus actions.

Most counsel will not recommend a writ unless your particular application is beyond the USCIS published normal processing times. I would recommend you have a consultation with the attorney who filed your application on your behalf. He or she would be in the best position to advise you. ]

We are filing many writs of mandamus and the government is opposing most now. We are fortunate that most courts appear to be sustaining most of the replies so mandamus remains a viable option.

Yes, you are. It usually costs between $3500 and $5000 to do that. We have filed many similar cases and usually within 60 days you get your case decided or an RFE.