I need to update my SharePoint 2010 farm with Service Pack 2 patch. Should i download and install only SP 2 patch or install all the previous cumulative updates before installing SP 2 patch?
Yes, Service Pack 2 contains all Cummulative Updates and Hot fixes before it..
Important: Be aware that June 2013 CU for SharePoint 2010 is a Post-SP2 CU. That means that SP2 does not include June 2013 CU.
Update July 31st: It is recommended to install June 2013 CU before SP2. June 2013 CU might not correctly identify the SP2 baseline. If SP2 has already been installed and June CU does not install you need to wait for August CU which will correctly identify the SP2 baseline.