Menorca is very beautiful during all year but it could be probaly not so mild in October.Depends on the weather when you're going there.Could be very windy and rainy or could be mild and nice.Weather is a little bit crazy at this season. I was living there some years ago, and I used to take baths until end of October.Water is always hotter after summer than before it, but depending on what you're used to(I'm used to cold water). .In my opinion the best season to go is in May.Spring with lots of flowers, still quiet and sunny.Anyway, in October, if the day it's sunny it is very nice to lie on the beach although you're not going to take a bath in the sea.And the most important ,it's absolutly not crowded.If you're looking for a nice and relaxing place, that's the one.
If you like hill walking, there are many beautiful places to do it,and you can walk from cave to cave. If weather is nice you could also rent a boat and discover some caves.In menorca there is a very special natural diversity .It is a Biosphere reserve.
In menorca , there are two different areas, north and South.On the North landscape is more rocky, ruggy and special,but beaches are also sandy, but bronw sand.On the South beaches are totally white sandy.Both areas have totally clear water.For bigger towns , go shopping, have dinner or going out, go to Mahon and Ciutadella.Both very special places.
Other musts are:Alaior,Binibeca(magic place with white and small houses),CAla Mesquida, Cala Coves,Son Bou,Cala Mitjana y Mitjaneta,Cala Macarella y Macarelleta,Cala en Turqueta,Cala Galdana, Nature reserve of S'albufera(a beautiful park with lots of paths, nature and fauna and a lagoon).All small places, but with superb landscape and beaches.
You also have to go to Cova en Xoroi, a disco built in the middle of a cliif.Go there to taste the sunset.
For food you have to taste "caldereta de langosta", a typical lobster stew, or shellfish paella and the excellent cheese. ALso very typical Gin.
It's is important to rent a car, to discover all places. Altough bus transportation is good in Summer, I think it won't be so good in October.And there aren't any buses to go to some places.
If you want to have some further information, you can visit the site:
http://www.emenorca.org/home_en.jsp?idi=en
You will love Menorca!