Regardless of how your lease is worded, you have the right to what courts have termed "quiet enjoyment." This is the right to enjoy your rented apartment or home undisturbed by others. However, within the scope of that right, landlords have the right to run their business, which includes maintaining the property and renting units. Putting a for-rent sign in front of an apartment in itself would not violate the quiet enjoyment provision, but related issues might.
If the for rent-sign results in prospective tenants ringing your doorbell to inquire about the premises, you could make a good argument your quiet enjoyment has been disturbed. If this is the case, ask your landlord to add an attachment to the sign that reads, "Do Not Disturb Occupants." If you are not being bothered by prospective tenants, the sign would not be interpreted as violating your peaceful enjoyment. If the sign results in your landlord showing your unit, take a few additional steps to determine whether the showings cross the line of violating your quiet enjoyment.
The first place to look for specific regulations pertaining to your unit is the lease. There may be language in this contract that specifically addresses the issue of showing the apartment before the end of your lease term. If there is none, look to local rent control legislation and state law. So long as there are no conflicts between these sources, the most restrictive rule will prevail.
Many state laws allow landlords to show a unit while it is still occupied. Unless a state law specifically prohibits this practice, it would be allowed so long as the landlord followed all related lease provisions, if any, and any local rent control laws. Many state and local laws do require notice before a landlord can show an occupied unit.
The District of Columbia and 20 states are without notice requirements for landlords showing units. Most of the remaining 30 states require 24 to 48 hours' notice to the tenant before a landlord can enter the unit. Some specify the landlord must include the purpose of the visit in the notice. A few states substitute the term "reasonable" or "advance" notice for a specific time frame. Many of the notice laws limit the hours and days of the week that a unit can be shown.
Rent control is a local law that limits how often and how much rent can be increased. Some rent control regulations also cover notice requirements to tenants. The rent laws in New York City, for instance, require the landlord to give five days' written notice to a tenant to show a unit. If your city has rent control, check with the local rent board for the notice rules.
Contact Your Landlord
If you believe your landlord is not following notice requirements for showings, or he is but the showings are so frequent you believe it is interfering with your quiet enjoyment, talk to him. Try to work something out that satisfies both his and your goals: getting the apartment rented and allowing you undisturbed enjoyment of your home. If a talk doesn't work, try a letter and reference the relevant state and local law provisions along with your reasons for believing your quiet enjoyment has been breached. As a last resort, consider contacting an attorney.