Should I allocate some of my retirement into a real estate fund?

First it helps to understand there are lots of types of real estate investments: 

- Stocks in companies that build homes (i.e. Lennar, DR Horton, Pulte),

 - Stocks in real estate managers and land holdings (i.e Jones Lang LaSalle, Plum Creek Timber, CBRE Group, Rayonier)

 - Real estate investment trusts that own portfolios of various types of real estate like apartments, hotels, medical buildings and retail

- and mutual funds that invest in all the above generally or in sectors.

So if you're a believer that home building and ownership is going to rise, maybe the way to play that is through the home builders and people who supply the stuff that they use like Home Depot, Lowes, Restoration Hardware and even Amazon. 

You can buy ETF's that give you exposure to the major homebuilders in one holding such as IShares US Home Construction (ITB) and SPDR Homebuildres ETF (XHB).   Fedelity has a managed fund that focuses on the industry (FSHOX) you can get with no load, and Franklin and Alpine Funds also offer sector open-end funds.

The sector has taken a short-term hit along with most of the market in the past couple months, but holding an allocation of 2-5% in an area like this wouldn't be a bad idea for a long-term investor who understands that homebuilders tend to be a "boom and bust" sector subject to wide waves of volatility. 

If you want real estate in a different form like commercial properties or land holdings, it might make sense to screen for suitable REIT's, ETF's or funds through Morningstar or on recommendation of qualified investment counsel.