[Dan.]

On top of your script:

pawn Код:

new CanChat[MAX_PLAYERS] = 1;

pawn Код:

public OnPlayerText(playerid, text[])
{
    if(CanChat[playerid] == 0)
    {
        SendClientMessage(playerid, FF0000, "You can send a message every 3 seconds!");
        return 0;
    }

    CanChat[playerid] = 0;
    SetTimerEx("AllowChat", 1000*3, false, "i", playerid);
    return 1;
}

pawn Код:

forward AllowChat(playerid);
public AllowChat(playerid)
{
    CanChat[playerid] = 1;
    return 1;
}