Is it legal to defame an apartment complex?

Kind of a random question, but is it legal to defame the name of an apartment complex?

Example:
In front (or right next to) their “Renew Today” signs I want to put signs of my own. These signs will say things like
“DO NOT SIGN A LEASE AT THIS COMPLEX”
“Don’t RENEW for $600. They will drop the rates right after and screw you TOO”
“Don’t get screwed”
“Horrible place to live”
“Charge unreasonable fees for no reason”
“Don’t let them LOCK you in”
“Liers”
“I bet they didn’t tell you about the horrible crime rate, did they?”
“Never fix anything”
“Read the WHOLE lease, expecially page 7”
“Charge overages for no reason”
“Read what others have to say: www.mysite.com"

Just poster board, hell I get it for free. I plan to keep these signs up over theirs for the duration of there “renew now” campaign.

Personally if I saw an apartment complex where a resident got so POed to where he posted signs, I don’t think I would want to live there.

Is this considered defimation of character? What if the statements are true? What if they are false? Can I be sued and\or jailed or is it free speech?