I know for a fact, that Lewes have asked to be away the weekends Brighton are at home. Can't see many, if any games conflicting.
Also as Lewes is east of Falmer, I can't see many away fans going there as the majority will come from the North and the West of Brighton. Think most will still go to Brighton itself as I am sure that is where they would buy their train tickets too (with the possible exception of knowlegable fans of London clubs). We shall see.
Plenty of us Spurs coming from parts of East Sussex/Kent for the friendly. The Lansdowne in Lewes sounds like a likely desination for us.